NORA study
The Neonatal and Obstetric Risk Assessment (NORA) study is a longitudinal prospective study conducted in KK Women’s and Children’s Hospital, Singapore, between September 1, 2010, and August 31, 2014. Participants are women with singleton pregnancies who attended antenatal clinics from 1st trimester. Women with viable singleton pregnancies confirmed by ultrasonography at less than 14 weeks of amenorrhea were considered eligible. Patients with chronic medical conditions known to be associated with adverse pregnancy outcomes (such as systemic lupus erythematosus) and pregnancies complicated by aneuploidy or foetal anomalies were excluded. These women were followed up throughout the antenatal course. Women with unsuccessful pregnancies (termination, miscarriage were also excluded. Gestational age was calculated from the estimated due date which was confirmed from the ultrasound scan in the 1st trimester based on crown rump length. A written informed consent was obtained from all participants. NORA study was approved by the SingHealth Centralised Institutional Review Board Ethics Committee, Singapore (CIRB Ref No. 2010/214/D). In the present analysis, 10 women who had pre-existing hypertension were excluded, making the final number of subjects 916.