Effects of smoking specified as cigarettes per day and maternal body mass index on hypertensive disorders of pregnancy.

ABSTRACT

BACKGROUND: We have previously described the prevalence in pregnancy of hypertension, proteinuria, oedema and preeclampsia/eclampsia according to maternal body mass index (BMI) and smoking status. We found that these disorders were less frequent among smoking women. To investigate whether this relationship is causal or a chance finding, we here present an analysis according to BMI and smoking specified according to the number of cigarettes consumed per day. MATERIALS AND METHODS: Data were from the German Perinatal Survey of 1998-2000. We classified women by BMI as underweight (BMI<18.5 kg/m2), normal weight (BMI 18.5-24.99 kg/m2), overweight (25.0-29.99 kg/m2), or obese (BMI≥30 kg/m2). Smoking was categorised as being a non-smoker or smoking 1-7, 8-14 or ≥ 15 cigarettes per day. Datasets from 433 669 singleton pregnancies with information on maternal BMI and smoking were included in the analysis. RESULTS: In all BMI categories hypertension, moderate to severe oedema, and preeclampsia/eclampsia became less prevalent with increasing maternal cigarette consumption. CONCLUSIONS: Dose-dependence was not convincing for proteinuria.Dose-dependence in the relationship between smoking and hypertensive disorders of pregnancy argues against a chance finding and for a causal relationship.