Antenatal care initiation
Information about the timing of antenatal care initiation was derived from electronic patient files (Micronatal®) of 10 midwifery practices in Rotterdam.22 The gestational age was determined by ultrasound. The gestational age at antenatal care initiation was used as a continuous variable indicating the gestational age in weeks at the first visit. In addition, to show the number of pregnancies that did not meet the recommendations of the Dutch Society of Obstetrics and Gynaecology (NVOG) for basic antenatal care at the time of data collection, we created a dichotomous variable indicating whether initiation was within or after 14 weeks gestational age.23