Cigarette smoking in pregnancy results in marked decrease in maternal hCG and oestradiol levels

We have examined serum levels of oestradiol (E2), sex-hormone binding globulin (SHBG) and human chorionic gonadotrophin (hCG) during early pregnancy in relation to smoking status at the time of sampling in a series of 147 women. Smoking was associated with significantly depressed serum levels of E2, SHBG and hCG: in smokers, E2 levels were on average 17.6% lower (P = 0.037), SHBG levels were 12.4% lower (P = 0.15), and hCG levels were 21.5% lower (P = 0.044). There appeared to be a steady decline in these values with increasing cigarette consumption. These lower hormone levels in smokers may explain certain adverse effects of smoking in pregnancy.