We obtained information on maternal age, ethnicity, educational level, parity, folic acid supplementation, and smoking by questionnaire at enrolment.11 (link) Maternal height and weight were measured and body mass index was calculated at enrolment. We measured maternal blood pressure with the validated oscillometric sphygmomanometer (OMRON Healthcare Europe B V, Hoofddorp, Netherlands) and documented the mean value of two blood pressure readings.23 (link)