The natural pattern of birth timing and gestational age in the U.S. compared to England, and the Netherlands

To examine cross-national differences in gestational age over time in the U.S. and across three wealthy countries in 2020 as well as examine patterns of birth timing by hour of the day in home and spontaneous vaginal hospital births in the three countries.

We did a comparative cohort analysis with data on gestational age and the timing of birth from the United States, England and the Netherlands, comparing hospital and home births. For overall gestational age comparisons, we drew on national birth cohorts from the U.S. (1990, 2014 & 2020), the Netherlands (2014 & 2020) and England (2020). Birth timing data was drawn from national data from the U.S. (2014 & 2020), the Netherlands (2014) and from a large representative sample from England (2008-10). We compared timing of births by hour of the day in hospital and home births in all three countries.

The U.S. overall mean gestational age distribution, based on last menstrual period, decreased by more than half a week between 1990 (39.1 weeks) and 2020 (38.5 weeks). The 2020 U.S. gestational age distribution (76% births prior to 40 weeks) was distinct from England (60%) and the Netherlands (56%). The gestational age distribution and timing of home births was comparable in the three countries. Home births peaked in early morning between 2:00 am and 5:00 am. In England and the Netherlands, hospital spontaneous vaginal births showed a generally similar timing pattern to home births. In the U.S., the pattern was reversed with a prolonged peak of spontaneous vaginal hospital births between 8:00 am to 5:00 pm.

The findings suggest organizational priorities can potentially disturb natural patterns of gestation and birth timing with a potential to improve U.S. perinatal outcomes with organizational models that more closely resemble those of England and the Netherlands.