The effect of smoking in pregnancy on maternal serum inhibin A levels.

To assess the effect of smoking on maternal serum, second-trimester inhibin A levels, we studied a database of 1277 women undergoing antenatal serum screening. There were 75 smokers, 1008 non-smokers and 194 women in whom smoking status was undetermined. All groups were matched for age, gestation and parity. The median level of inhibin A in smokers was 1.47 multiples of the normal gestation-specific median (MOM) as compared with 1.01 MOM in non-smokers and 0.95 MOM in the undetermined group. The increase was highly statistically significant (p<0.0001, Wilcoxon rank sum test, two-tail). On the basis of these results we conclude that if inhibin A is used as a marker, adjustment for maternal smoking status may be necessary.