Fertility. Women who smoke are more likely to be infertile or take longer to conceive than women who do not smoke. In addition, smokers are more liable to have an earlier menopause than are nonsmokers. Increased metabolism of oestrogens may not be the whole explanation.
Complications of pregnancy. The risks of spontaneous abortion, stillbirth, and neonatal death are approximately doubled. There are various placental abnormalities. The placenta is heavier in smoking than nonsmoking women and its diameter larger. The enlarged placenta and placental abnormalities may represent adaptations to lack of oxygen due to smoking, secondary to raised concentrations of circulating carboxyhaemoglobin.
The child. The babies of women who smoke are approximately 200 g lighter than those of women who do not smoke. They have an increased risk of death in the perinatal period which is independent of other variables such as social class, level of education, age of mother, race or extent of antenatal care. The increased risk rises two-fold or more in heavy smokers and appears to be entirely accounted for by the placental abnormalities and the consequences of low birthweight. Ex-smokers and women who give up smoking in the first 20 weeks of pregnancy have offspring whose birthweight is similar to that of the children of women who have never smoked.
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