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Antenatal care 

Antenatal care
Chapter:
Antenatal care
Author(s):

Janet Medforth

, Linda Ball

, Angela Walker

, Sue Battersby

, and Sarah Stables

DOI:
10.1093/med/9780198754787.003.0004
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Confirmation of pregnancy

There are a number of options for women wishing to confirm their pregnancy. A range of home pregnancy testing kits are available from pharmacies, and most pharmacies will carry out a test for a small charge.

GP surgeries also provide this service.

The tests are based on detecting the presence of β‎-human chorionic gonadotrophin (β‎-hCG) in the woman’s urine or blood. This hormone is secreted by trophoblast or placental tissue from around 7–10 days after conception.

Other signs of pregnancy are:

  • Amenorrhoea: absence of menstrual periods in a woman who normally experiences menstruation

  • Nausea and vomiting: common in the first trimester from 6 weeks’ gestation, peaking at around 10 weeks’ gestation and diminishing as the pregnancy reaches 12 weeks and beyond. It persists throughout pregnancy in some women

  • Frequency of micturition: increased urine production and pressure on the bladder due to the growing uterus

  • Tiredness: increased metabolic activity and rapid growth of uterine and placental tissue

  • Breast tenderness/changes: hormonal effects of oestrogen and progesterone. The breasts enlarge and become tender and heavier

  • Fetal movements: these are a late sign, appearing in the second trimester as the fetus grows and the uterus becomes a larger abdominal organ. Early movements feel like fluttering or bursting bubbles. First-time mothers notice these later (18–20 weeks) than those undergoing a second or subsequent pregnancy (16–18 weeks)

  • Pica: or craving for unusual foods, or combinations of foods—hormonal influences on the gastrointestinal tract alter the mother’s perception of taste.

Dating the pregnancy

Ascertain the following:

  • The first day of the LMP. This may be difficult to ascertain accurately, unless the woman is in the habit of recording this

  • The length of the menstrual cycle in days and its regularity

  • The number of days of bleeding and if the LMP was a normal bleed

  • The woman’s usual method of contraception and when this was stopped. If the LMP was a withdrawal bleed after oral contraceptive, this date is unreliable.

Calculate the EDD for a 28-day cycle by adding 7 days and 9 months to the date of the LMP. Make adjustments for shorter or longer cycles. (Antenatal care See also Taking a menstrual history, p. 20.)

Confirm the dates by ultrasound scan. Most women will be offered a scan at around 14 weeks’ gestation to coincide with serum fetal screening tests.

The earlier the scan, the more accurate the estimation of the fetal age. If the results differ from the menstrual date by >2 weeks, the scan date should be accepted as the correct date and the EDD adjusted accordingly.

Having accurate dates allows for correct interpretation of fetal screening tests and prevents unnecessary induction of labour for post-maturity.

Further reading

Debbie Chalk; North Somerset Community Partnership. Pregnancy testing standards. Available at: Antenatal carewww.nscphealth.co.uk/pregnancy-testing-standards-public-pdf.

NHS Choices. Doing a pregnancy test. Available at: Antenatal carewww.nhs.uk/conditions/pregnancy-and-baby/pages/pregnancy-test.aspx#close.

Adaptation to pregnancy

Increasing amounts of circulating hormones bring about pregnancy changes throughout the body, and all body systems are affected to a greater or lesser degree. The changes allow the fetus to develop and grow, prepare the woman for labour and delivery, and prepare her body for lactation.

The reproductive system

  • Most of the changes take place in the uterus, which undergoes hypertrophy and hyperplasia of the myometrium. The decidua also becomes thicker and more vascular.

  • Progesterone causes the endocervical cells to secrete thick mucus, which forms a plug, called the operculum, in the cervical canal, protecting the pregnancy from ascending infection.

  • Muscles in the vagina hypertrophy and become more elastic to allow distension during the second stage of labour.

The cardiovascular system

  • Due to the increasing workload, the heart enlarges.

  • Cardiac output increases to accommodate the increasing circulating blood volume.

  • Peripheral resistance is lowered, due to the relaxing effect of progesterone on the smooth muscle of the blood vessels, leading to a fall in BP.

  • To avoid aorto-caval compression, as the arterial walls are more relaxed, it is important to avoid placing the woman in an unattended supine position during the third trimester.

  • Blood flow increases in the uterus, skin, breasts, and kidneys, and blood volume increases by 20–50%, varying according to size, parity, and whether the pregnancy is singleton or multiple.

The respiratory system

  • Oxygen consumption increases by 15–20% at term.

  • Tidal volume increases by 40%.

  • Residual volume decreases by 20%.

  • Alveolar ventilation increases by 5–8L/min, four times greater than oxygen consumption, resulting in enhanced gaseous exchange.

  • The amount of air inspired over 1min increases by 26%, resulting in hyperventilation of pregnancy, causing carbon dioxide (CO2) to be removed from the lungs with greater efficiency.

  • Oxygen transfer to, and CO2 transfer from, the fetus are facilitated by changes in the maternal blood pH and partial pressure of CO2 (pCO2).

The urinary system

  • Renal blood flow increases by 70–80% by the second trimester.

  • The glomerular filtration rate (GFR) increases by 45% by 8 weeks’ gestation.

  • Creatinine, urea, and uric acid clearance is increased.

  • Glycosuria occurs as a result of the increased GFR and is not usually related to increased blood glucose.

  • The ureters relax under the influence of progesterone and become dilated. Compression of the ureters against the pelvic brim can lead to urinary stasis, bacteriuria, and infection of the urinary tract.

  • As the fetal head engages at the end of pregnancy, the bladder may become displaced upwards.

The gastrointestinal system

  • Nausea is experienced by 70% of pregnant women, beginning at around 4–6 weeks and continuing until 12–14 weeks.

  • Most women notice an increased appetite and an increased thirst in pregnancy.

  • Reflux of acid into the oesophagus, resulting in heartburn, is common.

  • Transit of food through the intestines is much slower and there is increased absorption of water from the colon, leading to an increased tendency to constipation.

Skeletal changes

  • Pelvic ligaments relax under the influence of relaxin and oestrogen, with the maximum effect in the last weeks of pregnancy.

  • This allows the pelvis to increase its capacity to accommodate the presenting part during the latter stage of pregnancy and during labour.

  • The symphysis pubis widens and the sacro-coccygeal joint loosens, allowing the coccyx to be displaced.

  • Whilst these changes facilitate vaginal delivery, they are likely to be the cause of backache and ligament pain.

Skin changes

  • Increased pigmentation of the areola, abdominal midline, perineum, and axillae due to a rise in pituitary melanocyte-stimulating hormone (MSH).

  • The ‘mask of pregnancy’, or chloasma, a deeper colouring of the face, develops in 50–70% of women, is more common in dark-haired women, and is exacerbated by sun exposure.

  • Striae gravidarum, commonly called stretch marks, occur as the collagen layer of the skin stretches over areas of fat deposition, e.g. breasts, abdomen, and thighs.

  • The stretch marks appear as red stripes and change to silvery white lines within 6 months of delivery.

  • Scalp, facial, and body hair become thicker. The excess is shed in the postnatal period.

The breasts

  • Breast changes are one of the first signs of pregnancy noticed by the mother. From around 3–4 weeks’ gestation, there is increased blood flow and tenderness; veins become more prominent, and the breasts feel warm.

  • Under the influence of oestrogen, fat is deposited in the breasts, increasing their size. The lactiferous tubules and ducts enlarge.

  • The pigmented area around the nipple darkens.

  • Progesterone causes growth of the lobules and alveoli and develops the secretory ability of these structures, ready for lactation.

  • Prolactin stimulates the production of colostrum from the second trimester onwards and, after delivery, is responsible for the initiation of milk production.

The endocrine system

All the endocrine organs are influenced by secretion of placental hormones during pregnancy.

  • Pituitary hormones: prolactin, adrenocorticotropic hormone (ACTH), thyroid hormone, and MSH increase. Follicle-stimulating hormone (FSH) and luteinizing hormone (LH) are inhibited. Oxytocin is released throughout pregnancy and increases at term, stimulating uterine contractions.

  • Thyroid hormones: total thyroxine levels rise sharply from the second month of pregnancy. The basal metabolic rate is increased.

  • Adrenal hormones: cortisol levels increase, leading to insulin resistance and a corresponding rise in blood glucose, particularly after meals. This makes more glucose available for the fetus.

  • Pancreas: due to increasing insulin resistance, the β‎ cells are stimulated to increase insulin production by up to four times during pregnancy. In women with borderline pancreatic function, this may result in the development of gestational diabetes, affecting 3–12% of pregnant women.

Further reading

McNabb M (2011). Maternal and fetal responses to pregnancy. In: Macdonald S, Magill-Cuerden J, eds. Mayes’ Midwifery: A Textbook for Midwives, 14th edn. Edinburgh: Baillière Tindall, pp. 397–410.Find this resource:

    Blood values in pregnancy

    Table 4.1 summarizes the main components of blood and shows the values prior to pregnancy and the changes as a result of the maternal adaptation to pregnancy.

    • The main feature is physiological anaemia due to increased plasma volume despite a rise in the red cell mass.

    • Decreasing plasma protein concentrations lead to lower osmotic pressure, contributing to oedema seen in the lower limbs during pregnancy. Moderate oedema, when not associated with disease, is an indicator of a favourable pregnancy outcome.

    Table 4.1 The main components of blood

    Component

    Non-pregnant

    Change in pregnancy

    Plasma volume

    2600mL

    3850mL at 40 weeks

    Red cell mass

    1400mL

    1650mL at 40 weeks

    Total blood volume

    4000mL

    5500mL at 40 weeks

    Haematocrit (PCV)

    35%

    30% at 40 weeks

    Haemoglobin (Hb)

    125–139g/L

    105–140g/dL at 40 weeks

    Protein

    65–85g/L

    55–75g/L at 20 weeks

    Albumin

    35–48g/L

    25–38g/L at 20 weeks

    Fibrinogen

    15–36g/L

    25–46g/L at 20 weeks

    Platelets

    150–400 × 103+/mm3

    Slight decrease

    Clotting time

    12min

    8min

    White cell count

    9 × 109/L

    10–15 × 109/L

    Red cell count

    4.7 × 1012/L

    3.8 × 1012/L at 30 weeks

    The booking interview

    The booking interview is a holistic assessment of the woman’s social, health, educational, and psychological needs and identifies those needing additional care. The purpose of the interview is to obtain a history and exchange information so that future care during pregnancy and birth can be planned. Both verbal and written information is given to enable parents to make informed decisions about screening tests.

    The following is a guide to the information given and obtained and the investigations that can be performed during this appointment. All the information gained and given should be carefully recorded. As the interview proceeds, it will be possible to establish a rapport and judge when it is appropriate to ask some of the more sensitive questions.

    Refer to the National Institute for Health and Care Excellence (NICE) antenatal care guidelines for conducting the booking interview.

    Social considerations

    • Confirm the woman’s name, age, and other relevant biographical details.

    • Is she in a stable supportive relationship?

    • What is her (and/or her partner’s) occupation?

    • Sensitive enquiry about whether she has experienced domestic abuse and if she is still in that relationship.

    Emotional and psychological considerations

    • Is the pregnancy planned?

    • Is she happy to be pregnant?

    • Has she any history of mental health problems?

    • Has she any concerns about her health or her pregnancy?

    Health considerations

    • Ask about present health and the current pregnancy. Are there any problems?

    • Ask about previous obstetric history, the number of pregnancies and births (gravida and parity), and whether these were normal.

    • Are her previous children healthy?

    • Ask about menstrual history, and calculate the EDD.

    • Ask about previous medical and family history such as twins, diabetes, epilepsy, hypertension, mental health issues, previous operations, and blood transfusions.

    • Verify the blood group and rhesus (Rh) status.

    • Measure the BMI and BP, and test the urine for proteinuria.

    Educational considerations

    Information and discussion to obtain consent for the following:

    • Offer screening for anaemia, red cell antibodies, hepatitis B, HIV, rubella antibodies, and syphilis

    • Offer screening for asymptomatic bacteriuria

    • Offer screening for Down’s syndrome

    • Offer an early ultrasound scan for gestational age assessment.

    Further reading

    National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. Appendix D: antenatal appointments (schedule and content). NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62/chapter/appendix-d-antenatal-appointments-schedule-and-content.

    Taking a sexual history

    • Unprotected sexual intercourse resulting in pregnancy may also put a woman at risk of contracting an STI.

    • Sensitive discussion about her past and current sexual health will determine the need for STI testing.

    • It is important to raise the issue of sexual health and STIs early in pregnancy to initiate diagnostic testing, appropriate referral to the sexual health service, and sexual health promotion, if applicable.

    • The rates of STIs in the UK have risen sharply in the past decade. The highest rates are found in women, gay men, teenagers, young adults, and black and ethnic minority groups.1

    • Whilst a programme of chlamydia screening in the 16- to 24-year age group has been instituted in the UK, this common STI is by no means limited to this age group and it is good practice to offer every pregnant woman urine-based screening, as a prevention for her ongoing, long-term sexual health and to prevent vertical transmission to her baby during vaginal birth.

    • Unrecognized/untreated STIs may be vertically transmitted to the baby, following rupture of the membranes and vaginal birth. (Antenatal care See Chapter 3 for more specific discussion on individual infections.)

    The discussion should include

    • Length of current relationship.

    • Number of sexual partners in the past 12 months.

    Symptoms

    • Change in vaginal discharge.

    • Vulval/vaginal soreness or irritation.

    • Intermenstrual bleeding.

    • Post-coital bleeding.

    • Pain during sex (dyspareunia).

    • Abdominal pain.

    • Contact of STI.

    • Past history of STI.

    • Contraceptive method(s).

    • Condom use.

    • Is she an IV drug user past or present?

    • Has she had sex with an IV drug user?

    • Has she been paid for sex?

    • Is her partner bisexual?

    • Has any partner been of non-UK origin, in this country or abroad?

    Investigations

    Investigations may include the following.

    Chlamydia

    • Endocervical swab.

    • Self-taken swab.

    • Urine test (first catch).

    Gonorrhoea

    • Endocervical swab, high vaginal swab: candidiasis (‘thrush’), Trichomonas vaginalis, bacterial vaginosis.

    • Viral culture swab: herpes, HPV.

    Blood testing

    • Syphilis.

    • HIV.

    • Hepatitis A.

    • Hepatitis B.

    • Hepatitis C.

    Other

    • Cervical screening:

      • Has the woman been called for screening at all? This will depend on the country in which she resides and the age at which the screening programme commences

      • If appropriate, has she been screened at all and when was her last test?

      • Has she ever been asked to attend for repeat testing within the normal recall time and has she ever had an abnormal result?

    • Has she had a colposcopy examination, and, if so, what was the outcome?

    Reference

    1Public Health England (2014). HIV and STIs. In: Public Health England. Health Protection Report: latest infection reports. Available at: Antenatal carewww.gov.uk/government/collections/health-protection-report-latest-infection-reports#hiv-and-sti.

    Principles of antenatal screening

    As science and technology advance, we are able to elicit more information about pregnancy, the mother, and the fetus than ever before. The scrutiny with which we examine every aspect of pregnancy has never been more detailed. It is very likely that further advances in these techniques will expose women to increasingly difficult choices and dilemmas. The midwife will need to be well prepared and informed to guide her clients through this process.

    A range of activities come under the banner of ‘antenatal screening’. Certain activities are a fundamental part of midwifery practice, e.g. measuring the fundal height, listening to the fetal heart, and the routine blood tests, including FBC, group and Rh factor, and maternal serum for rubella antibodies. We may classify these as low intervention, unlikely to cause any ethical concern. Other types of screening, such as those undertaken to detect a fetal abnormality, can lead to much moral difficulty.

    Aims of screening

    The whole pregnant population is screened because, although collectively this population has a low risk of abnormality, screening aims to identify those at higher risk, so that more specific diagnostic tests can be applied.

    Benefits of screening and diagnosis

    • Reduce fetal abnormality.

    • Reduce genetic reoccurrence.

    • Reduce the incidence of mental handicap.

    • Reduce the burden on family and society.

    • Increase resources for those disabled individuals who are not detected before birth.

    Adverse effects of screening and diagnosis

    • Anxiety provoked by screening procedures.

    • Psychological sequelae for parents.

    • Risks of diagnostic tests to the woman and fetus.

    • Risks to the woman of a late termination of pregnancy.

    • Risk of aborting a normal fetus.

    • Long-term effects on society’s attitude to the disabled.

    Implications

    • Inadequate counselling at the time of the test could mean that clients are not prepared for adverse outcomes, such as being recalled with a high-risk result or giving birth to an affected child after having a low-risk result from the screening test.2

    • No matter how good a test is technically, screening uninformed, unsupported clients by unprepared staff is a recipe for, at best, confusion and, at worst, great distress. This is avoidable.3

    Consent and counselling

    • Screening tests other than those performed in normal midwifery care are likely to reveal information for which parents need to be prepared and to result in decisions being made about the future of the pregnancy.

    • If, on consideration, parents decide not to take up the offer of tests, then this should be respected.

    • In practice, it is difficult to ensure that clients are aware of all the ramifications of tests, especially when so many are on offer.

    • Where informed consent has not been obtained and a positive result to a screening test is returned, the practitioner is vulnerable to litigation.

    • If a client’s language barrier or intellect makes understanding difficult, it may not be professionally acceptable to go ahead with tests.

    • The use of interpreters is problematic, but there is usually a protocol, and advice can be sought from a specialist midwife.

    • If the client is not mentally competent, then she cannot effectively give consent as an autonomous person. The principle of beneficence could be invoked to provide care that is in the best interests of the client. Paternalism may be justified in any number of circumstances, notwithstanding the limited mental capacity of the client.

    References

    2Public Health England (2015). NHS Screening Programmes: fetal anomaly. Available at: Antenatal carewww.gov.uk/government/uploads/system/uploads/attachment_data/file/456654/FASP_programme_handbook_August_2015.pdf.

    3Public Health England (2013, updated 2015). Fetal anomaly screening: providing services. Available at: Antenatal carewww.gov.uk/government/collections/fetal-anomaly-screening-providing-services.

    Screening for risk in pregnancy

    Risk screening during pregnancy aims to identify those women at risk, so that a suitable pattern of care can be planned for the pregnancy with the appropriate professional.

    For women deemed to be healthy and at low risk, midwife or midwife/GP care, based in the community, is a suitable alternative to consultant- or hospital-based care programmes.

    Assessment of risk should be ongoing, so that deviations from the normal or the development of complications can be identified at any stage of pregnancy and referral to appropriate care arranged. This assessment starts at the booking interview or initial appointment. For many women this takes place in their own home and is conducted by the community midwife.

    Women with any of the following need care over and above that recommended for low-risk, healthy women by the NICE guidelines:4

    • Cardiac disease, including hypertension

    • Renal disease

    • Endocrine disorder or diabetes requiring insulin

    • Psychiatric disorder (on medication)

    • Haematological disorder (including thromboembolic disease)

    • Epilepsy requiring anticonvulsant medication

    • Malignant disease

    • Severe asthma

    • Drug misuse (heroin, cocaine, ecstasy)

    • HIV or hepatitis B

    • Autoimmune disorders

    • Obesity—BMI 30kg/m2 or above (or underweight—BMI <18kg/m2)

    • Women at higher risk, e.g. age >40 or <14 years

    • Women who are particularly vulnerable or who lack social support.

    Women who have experienced any of the following in previous pregnancies are at higher risk:

    • Recurrent miscarriage (three or more)

    • Preterm birth

    • Severe pre-eclampsia, eclampsia, or HELLP (haemolysis, elevated liver enzymes, and low platelet count) syndrome

    • Rh isoimmunization or other significant blood group antibodies

    • Uterine surgery—Caesarean section, myomectomy, or cone biopsy

    • Ante- or post-partum haemorrhage on two occasions

    • Puerperal psychosis

    • Grand multiparity (>6)

    • A stillbirth or neonatal death

    • A small-for-gestational-age (SGA) infant (<5th centile)

    • A large-for-gestational age infant (>95th centile)

    • A baby weighing <2.5kg or >4.5kg

    • A baby with a congenital anomaly (structural or chromosomal).

    Reference

    4National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.

    The full blood count

    • An FBC obtained in the first trimester acts as a baseline against which all other measurements can be compared.

    • An FBC should be repeated at 28 weeks’ gestation to allow for correction of anaemia prior to term.

    • As pregnancy progresses, plasma volume expansion is greater than the corresponding rise in the red cell count; this leads to a haemodilution effect and the haematocrit falls, along with the Hb level. This is called physiological anaemia.

    • Apparent anaemia can be a sign of an excellent adaptation to pregnancy. The effect is greatest at around 30–32 weeks’ gestation.

    • Lower mean Hb concentrations are associated with higher mean birthweights, and higher mean Hb concentrations are associated with an increase in preterm delivery and low-birthweight babies.

    • Hb levels outside the normal UK range for pregnancy should be investigated, and iron supplementation considered if indicated.

    • The levels are 110g/L at first contact and 105g/L at 28 weeks’ gestation.

    • In order to correctly assess for anaemia, the impact of gestational age on plasma volume should be considered. Use of Hb level as a sole indicator of anaemia is not recommended.

    • Serum ferritin is the most sensitive single screening test to detect adequate iron stores. Using a cut-off point of 30 micrograms/L a sensitivity of 90% has been reported.5

    Reference

    5National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.

    ABO blood group and rhesus factor: anti-D prophylaxis for the Rh-negative mother

    At the initial appointment, as well as obtaining a full medical and obstetric history from the woman, venous blood is obtained so that the blood group, the Rh factor, and the presence of red cell antibodies can be determined. This test will identify women who are Rh-negative and who therefore require further antibody testing during pregnancy.

    Recording the blood group is necessary for future reference if the mother needs a blood transfusion around the time of birth. Group O is the most common blood type in the UK; 85% of individuals will also have the Rh factor and will therefore be Rh-positive.

    What is the Rh factor?

    • The Rh factor is a complex protein antigen carried on the surface of the red blood cell (RBC). It is inherited from three pairs of genes called cde/CDE. It is the pair named D that makes an individual Rh-positive and is likely to cause Rh isoimmunization.

    • Rh-negative women who carry an RhD-positive fetus may produce antibodies to the fetal RhD antigens after a fetomaternal haemorrhage. These antibodies may cross the placenta in future pregnancies, causing haemolytic disease of the newborn (HDN) if the fetus is RhD-positive.

    • HDN can range in severity from stillbirth, severe disabilities, or death to anaemia and jaundice in the neonate. To prevent this from occurring, Rh-negative women who have experienced a suspected or known sensitizing event during pregnancy are given an IM injection of anti-D immunoglobulin (Ig) to prevent antibody production.

    • The anti-D Ig works by coating the fetal red cells that have escaped into the mother’s circulation so that they cannot be recognized by her immune system. This prevents maternal antibody formation and thus protects the RhD-positive fetus of any subsequent pregnancy.

    What is a sensitizing event?

    Very occasionally Rh-negative women may produce antibodies as a result of a mismatched blood transfusion, but fetal red cells from the RhD-positive fetus can cross the placenta and enter the woman’s circulation at any time during the pregnancy, particularly if events cause bleeding from the placental site.

    ►► The most important cause of RhD immunization is during pregnancy where there has been no overt sensitizing event. Sensitizing events include:

    • Threatened abortion and abortion after 12 weeks’ gestation

    • Chorion villus sampling

    • Threatened abortion, spontaneous abortion, termination of pregnancy where bleeding is repeated, heavy, or associated with abdominal pain

    • Amniocentesis

    • Antepartum haemorrhage (APH)

    • Abdominal trauma

    • Hypertension

    • Eclampsia

    • Traumatic delivery, including Caesarean section

    • Placental separation during the third stage of labour

    • Manual removal of the placenta.

    In the Rh-negative woman, these events should be followed by prophylactic administration of anti-D Ig. The British Committee for Standards in Haematology (2014) has reviewed the advice that recommends that all Rh-negative women receive prophylactic anti-D.6

    • The treatment regimen may vary, according to local costs, for instance being able to offer a one-visit option, staff costs of administration, and the cost of the Ig.

    • The options are:

      • 250IU below 12 weeks, and 500IU at 28 and 34 weeks’ gestation;

      • 1000–1650IU at 28 and 34 weeks’ gestation

      • a single dose of 1500IU at 28–30 weeks, as well as cover for sensitizing events.

    • If a sensitizing event is suspected, Kleihauer’s test (on maternal venous blood) estimates the amount of fetal red cells in the maternal circulation, and a measured dose of anti-D can be administered. A 500IU dose is enough to deal with an 8mL transplacental transfusion of fetal blood. Prior to 20 weeks’ gestation, it is usual to give 250IU as a prophylactic dose.

    • Blood samples are taken within 1h of delivery from the Rh-negative mother to test for maternal antibodies and fetal cells (Kleihauer’s).

    • Also from the neonate, to discover its blood group and Rh factor. If the neonate is Rh-negative, then the mother requires no further anti-D Ig.

    • In the event of an intrauterine death where no sample can be obtained from the baby, an appropriate dose of prophylactic anti-D Ig should be administered to D-negative, previously non-sensitized women within 72h of the diagnosis of the intrauterine death, irrespective of the time of subsequent delivery (Grade 1C).

    • Where intraoperative cell salvage (ICS) is used during a Caesarean section in D-negative, previously non-sensitized women and where the cord blood group is confirmed as D-positive (or unknown), a minimum dose of 1500IU anti-D Ig should be administered following the reinfusion of salvaged red cells, and a maternal sample should be taken for estimation of feto–maternal haemorrhage (FMH) 30–45min after reinfusion in case more anti-D Ig is indicated. It is important that clinicians inform the transfusion laboratory if ICS has been used to ensure that the correct dose of anti-D Ig is issued (Grade 2C).

    • It is the midwife’s responsibility to carry out tests during pregnancy to identify women who require anti-D prophylaxis. A full explanation should be given to the woman and her consent obtained for any tests or administration of anti-D Ig.

    Reference

    6Qureshi H, Massey E, Kirwan D, et al.; British Society for Haematology (2014). BSCH guideline for the use of anti-D immunoglobulin for the prevention of haemolytic disease of the fetus and newborn. Transfus Med24: 8–20.Find this resource:

    Screening for Down’s syndrome risk

    The incidence of Down’s syndrome is approximately 1:600 to 1:700 across the age range of the childbearing population. There are variations in incidence according to maternal age:

    • At 18 years of age, the incidence is 1:2300

    • At 35 years, it is 1:200 to 350

    • At 40 years, it is 1:100

    • At 45 years, it is 1:45.

    Taking age as the only risk factor would mean that <30% of affected fetuses would be detected by diagnostic testing, as it would not be appropriate to offer amniocentesis to all women.

    Down’s risk screening was developed in the 1980s to enable all pregnant women to be given an estimate of the individual risk if they choose to be screened. The risk is calculated by examining a combination of the following factors:

    • Maternal age

    • Gestational age in completed weeks

    • Maternal body weight

    • Serum screening.

    Maternal serum screening

    • This enables examination of a combination of hormones and proteins present in the maternal bloodstream during early pregnancy.

    • Levels vary according to the fetal gestational age.

    • Abnormally low or high levels are linked to genetic, chromosomal, and structural abnormalities of the fetus.

    • High levels of α‎-fetoprotein (AFP) are associated with NTDs, and low levels with Down’s syndrome.

    • NTDs can be confirmed by ultrasound scan and also amniocentesis.

    Recommended screening: aims

    • Screening for Down’s syndrome should be performed by the end of the first trimester (13 weeks 6 days), but provision should be made to allow later screening (which could be as late as 20 weeks 0 days) for women booking later in pregnancy.

    • The ‘combined test’ (nuchal translucency, β‎-hCG, pregnancy-associated plasma protein-A) should be offered to screen for Down’s syndrome between 11 weeks 0 days and 13 weeks 6 days.

    • For women who book later in pregnancy the most clinically and cost-effective serum screening test (triple or quadruple test) should be offered between 15 weeks 0 days and 20 weeks 0 days.

    • When it is not possible to measure nuchal translucency, owing to fetal position or high BMI, women should be offered serum screening (triple or quadruple test) between 15 weeks 0 days and 20 weeks 0 days.

    Sensitivity

    • The sensitivity of the test is a measurement of how many affected fetuses are detected. This means that around 5% of women having the test will be recalled for further investigation.

    • The false-positive rate is between 2.6% and 5%. This percentage of women will be carrying a normal baby despite a high-risk screening result. About 60 women will be recalled for every affected baby diagnosed.

    • The false-negative rate is 20%. This percentage of women will be carrying an affected baby despite a low-risk screening result.

    Results and consequences of screening

    • Offer diagnostic testing if a woman’s screening result is 1:10 to 1:210.

    • If the result is 1:210+, then advise the woman that her screening result is low risk.

    • Provide information about what the test involves, how the risk is calculated, and what is meant by a risk factor.

    • There needs to be an understanding that low risk is not ‘no risk’ and that any woman could be the ‘one’ of the 1:800.

    • Explain the nature of the diagnostic test and the risk of miscarriage from this test (1%).

    • Discuss options following a diagnosis of Down’s syndrome and provide non-directive support to the decision to choose termination or continuation of the pregnancy.

    Further reading

    National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.

    Sickle-cell anaemia

    Haemoglobin is a complex molecule, with the ability to absorb oxygen easily and reversibly. The molecule is composed of iron and protein. The protein structure is inherited and is the part affected in haemoglobinopathies, being either abnormal or partly missing.

    A normal RBC in an adult is filled with adult Hb. Everyone inherits their Hb type from their parents, half of the responsible gene copies from each, and the usual type is HbAA.

    Sickle-cell trait

    • Sickle Hb (abbreviated HbS) has an abnormality of the protein part of the molecule.

    • An individual inheriting HbS from one parent and HbA from the other will have Hb type HbSA.

    • This is known as the sickle-cell trait.

    • The RBCs of such individuals will function normally, and they will have few, if any, symptoms.

    • However, these individuals have a 50% chance of passing this type of Hb on to their children.

    • This condition confers immunity from the malaria parasite, which explains the prevalence of the condition in areas where malaria infection is endemic.

    • Due to population movement, individuals can inherit this type of Hb, even if their ancestry is from malaria-free areas.

    Sickle-cell anaemia

    • In this case, the individual inherits HbS from both parents, so the Hb type is HbSS.

    • RBCs containing only HbSS react to hypoxia, acidosis, or dehydration by changing shape, from the usual biconcave disc to a crescent or sickle shape.

    • These RBCs are more fragile and easily damaged and will clump together, blocking capillaries.

    • Painful crises are provoked by the blockage of small blood vessels.

    • The overall effect is that the RBCs are haemolysed, rapidly causing chronic haemolytic anaemia.

    Effects on childbearing

    Increased incidence of:

    • Subfertility

    • Spontaneous miscarriage

    • APH

    • Antenatal hospitalization

    • Impaired placental function

    • PIH

    • Pulmonary and renal problems

    • Phlebitis and thromboembolic events

    • Fetal growth restriction

    • Premature labour

    • Caesarean birth

    • Infection

    • Perinatal mortality.

    Women with this type of anaemia need to be well hydrated during labour and need careful monitoring to avoid hypoxia should an anaesthetic be required.

    Screening

    It is estimated that there are 12 000–15 000 affected individuals and over 300 infants born with sickle-cell disease (SCD) in the UK each year who are diagnosed as part of the neonatal screening programme. There are approximately 100–200 pregnancies in women with SCD per year in the UK.

    • Information about screening for SCDs and thalassaemias, including carrier status and the implications of these, should be given to pregnant women at the first contact with a health-care professional.

    • Screening for SCDs and thalassaemias should be offered to all women as early as possible in pregnancy (ideally by 10 weeks). The type of screening depends upon the prevalence and can be carried out in either primary or secondary care.

    • If the woman has not been seen preconceptually, she should be offered partner testing. If the partner is a carrier, appropriate counselling should be offered as early as possible in pregnancy—ideally by 10 weeks of gestation—to allow the option of first-trimester diagnosis and termination if that is the woman’s choice.

    Further reading

    Royal College of Obstetricians and Gynaecologists (2011). Sickle cell disease in pregnancy, management of (Green-top guideline No. 61). Available at: Antenatal carewww.rcog.org.uk/en/guidelines-research-services/guidelines/gtg61/.

    Thalassaemia

    In this recessively inherited condition part of the Hb protein is missing. The protein is made from structures called α‎ and β‎ chains. As several genes are responsible for the structure of these chains, it is possible to have varying degrees of the condition.

    β‎-thalassaemia minor

    The individual inherits one normal gene from one parent and one affected gene from the other parent. This is a carrier state and has little effect on health, other than mild anaemia. Affected individuals can pass on the defective gene to their children.

    β‎-thalassaemia major

    The individual inherits defective genes from both parents and can make no, or very few, β‎ chains, so does not produce sufficient Hb. This results in severe anaemia, requiring regular blood transfusions and therapy to remove excess iron from the blood.

    α‎-thalassaemia

    People with normal Hb carry four α‎ globin genes, two from each parent. α‎-thalassaemia results from the deletion of one or more of these genes. Table 4.2 shows the result of deletions of one or more of the genes and the effect on the type of Hb produced.

    Table 4.2 Effect of gene deletions

    Gene deletions

    Diagnosis

    Adult blood

    (aa/–a)

    α‎2 thalassaemia

    Normal

    (aa/– –) or (a–/a–)

    α‎1 thalassaemia

    Small RBCs

    (–a/– –)

    Hb H disease

    Moderate anaemia

    (– –/– –)

    Hydrops fetalis

    Not compatible with life

    Screening for thalassaemia

    • As with sickle-cell anaemia, antenatal screening should be offered to all pregnant women, as recommended.7

    • A routine FBC will identify women with hypochromic, microcytic anaemia. Hb electrophoresis will then identify the underlying haemoglobinopathy.

    • Knowing the carrier state of each parent allows counselling about the risks to the fetus of being a carrier or having the disease.

    • Haemoglobinopathy screening is carried out on newborns as part of the neonatal blood spot test.

    Impact of maternal thalassaemia major on pregnancy

    • Depends on the degree of chronic anaemia and the oxygen deprivation that results from this.

    • If the woman cannot adequately meet her own oxygen needs, the fetus becomes progressively hypoxic.

    • Fetal survival may be threatened with spontaneous abortion, intrauterine growth restriction (IUGR), preterm birth, or intrauterine death.

    • Women who are carriers (α‎- and β‎-thalassaemia trait) may be only mildly anaemic and require only supportive care.

    Management of thalassaemia major during pregnancy

    • Specialist medical and obstetric supervision is required.

    • Blood transfusion therapy continues.

    • Use of iron chelation therapy is not without risk and needs to be individualized. Desferrioxamine should be avoided in the first trimester, owing to a lack of safety data. It has been used safely after 20 weeks of gestation at low doses.7

    • Iron deposition in the pancreas and thyroid increases the risk of the woman developing diabetes, so a glucose tolerance test would be indicated.

    • Blood transfusion, whilst vital, increases the risk of cardiac failure, which, in turn, increases the risk of maternal mortality by as much as 50%.

    Women who are asymptomatic before pregnancy may find the added stresses of pregnancy can cause deterioration of their health status. The more severe the syndrome, the more significant the consequences for the woman and fetus.

    Reference

    7Royal College of Obstetricians and Gynaecologists (2014). Management of beta thalassaemia in pregnancy (Green-top guideline No. 66). Available at: Antenatal carewww.rcog.org.uk/globalassets/documents/guidelines/gtg_66_thalassaemia.pdf.

    Antenatal examination

    The purpose of the antenatal examination depends on the length of gestation at which it takes place.

    NICE (2008) has published guidelines for the routine care of women who are experiencing a healthy, low-risk pregnancy.8 The recommended number of scheduled appointments is determined by parity and the function of the appointment. For the primigravida with an uncomplicated pregnancy, ten visits are adequate, and, for the parous woman with an uncomplicated pregnancy, seven visits should be adequate.

    Throughout the antenatal period, be alert to the signs and symptoms of conditions that affect the health of the mother and fetus such as pre-eclampsia, diabetes, and domestic abuse.

    • After the first appointment or booking visit, use the next visit to review, discuss, and document the results of all the screening tests undertaken earlier and to identify women who need additional care.

    • Arrange further investigations for a woman with a Hb level of <110g/L, and offer iron supplementation.

    • At each visit, measure the BP and test the urine for protein.

    • At each visit, be prepared to ask questions; give information and discuss issues about the woman’s physical and emotional/psychological well-being; and use the available time to provide education, supported by antenatal classes and written information.

    • After 20 weeks, measure and plot the symphysis–fundal height (SFH) to detect small- or large-for-dates pregnancies.

    • If requested by the mother, auscultate the fetal heart sounds by handheld ultrasound.

    • Offer anti-D prophylaxis to Rh-negative women at 28 and 34 weeks’ gestation.

    • Offer a second screening for anaemia and atypical red cell antibodies at 28 weeks’ gestation. Investigate a Hb level of <105g/L and provide iron supplementation if necessary.

    • At 36–37 weeks’ gestation, confirm the lie and presentation of the fetus, and offer external cephalic version for women whose babies are in the breech position.

    • If an earlier report showed the placenta extending over the internal cervical os, a further scan should be arranged and reviewed at 36 weeks.

    • A further appointment should be arranged for women who have not given birth by 41 weeks, to offer a membrane sweep and induction of labour if this is unsuccessful.

    Reference

    8National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.

    Abdominal examination

    An abdominal examination can be carried out at any stage of pregnancy and is used to determine the progress of pregnancy or labour and fetal well-being.

    The examination is in three parts: inspection, palpation, and auscultation.

    Ask for the woman’s consent before the examination. Make her comfortable on the examination couch, lying supine with her head supported by one pillow. Her arms should be relaxed by her sides. Expose her abdomen, but use a sheet or towel to cover her pelvic area and legs, preserving her privacy and dignity.

    Inspection

    • Inspect the abdomen for size and shape. In the primigravida, the shape is oval, due to abdominal muscle tone. In the parous client, the shape may be more rounded.

    • There may be a saucer-shaped depression below the umbilicus if the fetus is presenting in an occipito-posterior position.

    • A heart-shaped uterus may indicate a transverse lie.

    • The umbilicus may protrude, and the linea nigra, which is the pigmented midline of the rectus sheath, may be apparent.

    • Other abdominal scars may be apparent, as will striae gravidarum or stretch marks, which are pink at first, turning to silvery white as they age.

    • Size should indicate the stage of pregnancy, which will be confirmed by measuring the SFH.

    • Observe for fetal movements—this confirms a live fetus.

    Palpation

    • Serial SFH measurements should be recorded at each antenatal appointment from 24 weeks’ gestation.9

    • Measure using a non-elastic tape measure.10

    • To enable an accurate identification of the uterine fundus, use both hands to locate the fundus.10

    • Use the tape measure with the centimetres on the underside to reduce bias, and measure from the top of the fundus to the top of the symphysis pubis, keeping the tape in contact with the skin.10

    The measurement should be plotted on a customized chart to improve prediction of an SGA infant.9

    • The lie of the fetus is normally longitudinal, with the long axis of the fetus lying along the long axis of the mother.

    • The presenting part is normally the fetal head. Breech presentation occurs in approximately 3% of pregnancies at term.

    • Determine the position of the fetus:

      • The position of the occiput can be found by locating the fetal back, which feels smooth and firm and will lie anteriorly on the left or right side of the uterus if the occiput is anterior

      • In posterior position, the back may be felt in the left or right flank, or it may not be palpable. If fetal limbs are felt on both sides of the midline, it is likely that the fetus is lying in an occipito-posterior position.

    • Establish the relationship of the presenting part to the pelvic brim. The fetal head is engaged in the pelvis when the widest diameter of the fetal head has entered the pelvic brim.

    Auscultation

    • Hearing the fetal heart will confirm that the fetus is alive, but it does not have any proven predictive value. Routine listening is not recommended, but if the mother requests it, auscultation may provide reassurance.

    • Explain the findings of the examination to the mother and record them in her notes.

    References

    9Royal College of Obstetricians and Gynaecologists (2014). The investigation and management of the small-for-gestational-age fetus (Green–top guideline No. 31). Available at: Antenatal carewww.rcog.org.uk/globalassets/documents/guidelines/gtg_31.pdf.

    10Perinatal Institute. Fetal growth: fundal height measurements. Available at: Antenatal carewww.perinatal.org.uk/fetalgrowth/FundalHeight.aspx.

    Further reading

    National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.

    Monitoring fetal growth and well-being

    As part of the overall antenatal assessment, the midwife is responsible for monitoring the growth and well-being of the fetus. Maternal well-being is the best indicator of fetal well-being, so evaluate the mother closely, looking for any problems that are likely to affect the fetus, e.g. hypertension, infection, diabetes, and environmental factors such as smoking, substance misuse, and dietary inadequacies.11

    • Ask about fetal patterns of movement and activity. All fetuses are active at some stage during a 24h period. The standard is to ask whether there are ten movements in a 12h period. Ask about strength of movements. This may change towards the end of pregnancy, as the fetus has less room to move about. Determine whether the mother is aware of all of the fetal activity.

    • Most mothers tend to know their baby’s activity pattern well. Ask them to report any concerns, such as reduced activity, especially after 40 weeks’ gestation.

    • If, during an antenatal visit, a mother reports diminished or absent movements, listen to the fetal heart with a Pinard stethoscope or an ultrasound transducer, and reassure the mother. (Intrauterine death is an uncommon, but possible, occurrence. If you do not hear the fetal heart, explain this in an honest and sensitive way and make arrangements to confirm the absence of the heartbeat by ultrasound scan.)

    • If a mother seeks advice over the telephone, you may want to arrange a cardiotocograph (CTG) of the fetal heart. This would be carried out in hospital and a non-reassuring trace referred to the obstetrician.

    • Carry out an abdominal examination at prescribed times, according to whether the mother has been assessed as low or high risk. A more accurate assessment of fetal growth can be obtained if the same person examines the mother on each occasion.

    • Overall growth of the uterus is estimated and the fundal height measured in centimetres. This should correspond roughly to the number of weeks’ gestation, plus or minus 2cm, taking into account maternal height and build.

    • Assess the volume of amniotic fluid surrounding the fetus and note increased or diminished amounts. Each pregnancy is assessed on its individual merits and over- or underproduction of amniotic fluid may be pathological or entirely innocent. If you are concerned, refer the woman to an obstetrician.

    • When IUGR or large-for-gestational-age fetuses are suspected, decide whether to refer for further investigation.

    • A large-for-date uterus may be due to a multiple pregnancy. The advent of routine dating scans has meant that multiple pregnancy is now diagnosed early, unless there has been an operator error or the woman has declined a scan.

    • An ultrasound scan may be arranged, but take care not to make the mother overanxious. These conditions are often overdiagnosed, leading to much unnecessary worry for mothers.

    • A scan to measure the head-to-abdomen ratio, performed on >1 occasion, will distinguish between symmetrical and asymmetrical growth restriction.

    • Scans estimating fetal weight are not reliable enough to predict an accurate birthweight, but they do provide a reasonable estimate to within 500g on either side of a given figure.

    Reference

    11National Institute for Health and Care Excellence (2008). Antenatal care for uncomplicated pregnancies. NICE guidelines CG62. Available at: Antenatal carewww.nice.org.uk/guidance/cg62.