Key messages

• Peripheral vasodilatation occurs early in pregnancy, probably mediated by endothelium-dependent factors. These include nitric oxide synthesis upregulated by estradiol and possibly vasodilatory prostaglandins. To compensate, cardiac output increases by 40 per cent during pregnancy.

• Labor is associated with a further increase in cardiac output. Following delivery there is an immediate rise in cardiac output owing to the relief of inferior vena caval obstruction and contraction of the uterus which empties blood into the systemic circulation.

• Oxygen consumption is increased by about 20 per cent and the maternal metabolic rate by 15 per cent.

• The plasma volume increases progressively throughout normal pregnancy. Most of the 50 per cent increase occurs by 34 weeks and is positively correlated with the birth weight of the baby.

• There is physiological sodium (and water) retention during pregnancy. Eighty per cent of pregnant women develop some edema, particularly toward term, and it is not always a pathological sign.

Sleep Apnea

Sleep Apnea

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