US pregnancies shorter than those in England, the Netherlands
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Pregnancies in the United States tended to be shorter, and deliveries occurred at different times of the day compared with those in England and the Netherlands, data published in PLOS ONE showed.
“I had long been interested in the natural timing of birth and the degree to which interventions might alter that timing,” Eugene Declercq, PhD, a professor of community health sciences at Boston University, told Healio. “A change to the U.S. Standard Certificate of a Live Birth that added time of day provided a foundation for this analysis. To add to the study’s generalizability, I worked with colleagues in two countries — England and the Netherlands — that had large numbers of home births and similar data. I had also been documenting the changes in gestational age in the U.S. and thought combining the two measurements in home and hospital births made a sensible pairing.”
Declercq and colleagues collected birth data available from population-based birth databases from each country to evaluate changes in gestational age at delivery from 1990 to 2020. For time of delivery, the researchers used birth certificate data from the U.S. — where all states adopted birth time on certificates by 2016. In England and the Netherlands, birth time data were collected from a 2010 and 2014 study, respectively.
The researchers also evaluated setting of delivery (ie, hospital or home birth).
In the U.S., mean gestational age at delivery decreased over time from 39.1 weeks in 1990 to 38.5 weeks in 2020. Nearly half (48%) of U.S. births in 1990 occurred at 40 weeks’ gestation or later, while only 30% met that benchmark in 2020.
Data from 2020 showed that 76% of U.S. births occurred before 40 weeks’ gestation; in the Netherlands and England, 56% and 60% of births, respectively, occurred before 40 weeks’ gestation.
Among births delivered before 37 weeks’ gestation, the most home births occurred between 1 a.m. and 5:59 a.m. and the fewest occurred between 2 p.m. and 4:59 p.m. in all three countries.
In England and Netherlands, hospital births occurred at about the same times as home births. In the U.S., however, hospital births were most common between 7 a.m. and 5 p.m. regardless of whether labor was induced or augmented.
“Since the U.S. appears to be the outlier in timing of low-risk hospital births and the U.S. also has generally poorer outcomes than the comparison countries, we might want to consider organizing care to better take advantage of the natural timing of births and length of gestation rather than have a system that seems to try to make timing conform to business hours,” Declercq said.
Because the study was conducted without funding and by volunteer researchers, future research on the topic should be conducted with more formal resources, Declercq said.