Study population
There were 10,366 births that underwent a prenatal ultrasound >28 weeks’ gestation without major anomalies during our study period, of whom approximately one third (3,418) had available kindergarten-age Early Development Index scores (due to the three-year duration of testing waves across the province). Of these, 17 fetuses could not be assigned an estimated fetal weight using the WHO chart because their gestational age was beyond that covered by that chart.
As expected given the higher risk obstetrical population seen at our tertiary referal centre, our ultrasound population had a moderately higher risk profile than the overall British Columbia population. Women in our study population were slightly older at delivery (Mean 33 versus 30 years), more likely to be nulliparous, with slightly higher cesarean delivery rates and higher rates diabetes and hypertension (Table 1 ). Birthweights of babies our study cohort were also slightly lower. Median EDI scores were similar (41.7 in our study cohort; 41.5 in the BC population), as were rates of identified vulnerability on the EDI (29.8% study cohort; 29.7% general population). Our study cohort had slightly higher rates of special needs designation (3.9% versus 2.7%). As expected, developmental vulnerability and special needs designation was more common among infants born at younger gestational ages (Table S1 ).