A morphometric study of maternal smoking on apoptosis in the syncytiotrophoblast

Objectives: To study syncytiotrophoblast apoptosis in the placenta of smoking and non-smoking pregnant women. Methods: Twelve neonates, pregnancies and placentas were available for study. Eight mothers smoked during pregnancy and the remaining four were non-smokers used as control subjects. The main outcome measure was the apoptotic syncytiotrophoblast index for each group. Apoptosis was detected by immunohistochemistry using the TUNEL method and quantitatively measured using a Merz grid. The apoptotic syncytiotrophoblast index was calculated as the ratio of mean apoptotic labeling to percent terminal villus area using high-power field microscopy. Results: Significant differences in apoptotic syncytiotrophoblast index were observed between the control group (15.06 +/- 3.72) and the smoker group (1.66 +/- 1.74) (P < 0.0001, Mann-Whitney test), but no differences were detected in clinical or morphometric data between groups. Conclusions: The human placental syncytiotrophoblast undergoes apoptosis and this process is associated with inhibition of apoptosis by the smoking habit. The same way as the presence of trophoblast apoptosis is associated with modifications of the maternal-fetal exchange, the inhibitory effect of the smoking habit on syncytiotrophoblast could be responsible for the poor prognosis of pregnancy in the presence of maternal smoking. (C) 1998 International Federation of Gynecology and Obstetrics.