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Physiological changes of normal pregnancy 

Physiological changes of normal pregnancy

Physiological changes of normal pregnancy

David J. Williams

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date: 23 April 2017

Almost every maternal organ system makes a physiological adaptation to pregnancy that is required for optimal pregnancy outcome. An understanding of these adaptations brings insight into the aetiology and management of gestational syndromes, and also helps the clinician to advise women with pre-existing chronic illness about the risks and consequences of a pregnancy.

Physiological adaptations in pregnancy—these include (1) cardiovascular—cardiac output increases 50%; (2) respiratory—oxygen consumption increases 20%; and (3) renal—glomerular filtration rate increases 55%.

Biochemical and endocrine changes in pregnancy—gestational changes alter the normal ranges for many important metabolic and endocrine laboratory tests, including (1) serum creatinine, urea—both decreased; (2) cholesterol and triglycerides—both increased; (3) liver blood tests—alkaline phosphatase increased up to four fold; and (4) thyroid function tests—free thyroxine and tri-iodothyronine levels fall, thyroid-stimulating hormone (TSH) levels rise. Awareness of these changes is essential, both for recognition of disease in pregnancy and to prevent inappropriate pursuit of test results that are normal in pregnancy.

Long-term implications of pregnancy syndromes—conditions such as pre-eclampsia and gestational diabetes mellitus are abnormal responses to pregnancy that resolve after delivery, but herald similar complications, i.e. hypertension and diabetes mellitus, in later life.

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