Smoking and its effect on maternal plasma volume during and after normal pregnancy.

Smoking during pregnancy decreases birthweight significantly. The mechanisms causing this decrease have not yet been clarified. Plasma volume (expansion) is positively related to birthweight. There are indications that plasma volume expansion in pregnancy is lower among smokers. A group of healthy women (n = 70) producing healthy mature babies after an uncomplicated pregnancy was studied. No difference in plasma volume was observed between non-smokers and smokers during and after pregnancy. It is unlikely that the growth-depressing effect of smoking during pregnancy is mediated by an influence on plasma volume expansion.