The first two months of COVID-19 lockdown saw about 4% fewer preterm births across 18 upper- and middle-income countries than expected, according to a meta-analysis in Nature Human Behavior.
In addition, there were 3% fewer preterm births in the third month of lockdown.
Researchers with a host of institutions across the world estimate that there were about 50,000 fewer preterm births in those months than historical data would predict.
Researchers collected data from 26 countries altogether, and lower- to middle-income countries (LMICs) didn’t fare as well. For instance, Nepal and Uruguay reported increases in preterm births of 11% to 30%.
And even in the U.S., where preterm births declined, that wasn’t the case throughout the country, with the study stating that California fell within the 11% to 30% range of increases in preterm births. The findings do not address the reasons preterm birth rates declined during this period.
“Understanding the underlying pathways linking lockdown with the reduction in preterm births could have implications for clinical practice and policy,” the meta-analysis said, adding that the findings highlight “the need to develop further capacity for high-quality and appropriate standardized data collection in LMICs.”
The study is huge, involving over 100 scientists across the world and data on about 52 million births. Researchers created a model of the expected rate of preterm births in each country by examining data from 2015 to 2020.
“This decrease in preterm births did not appear to be linked with an increase in stillbirths in most settings,” the study said. “Consistent evidence of an increase in stillbirths was only observed in Brazil following a lockdown, the causes of which certainly warrant further exploration.”
The study found “substantial reductions” in preterm births in Australia, Israel, Canada, Spain, Sweden and the U.S. Some high-income countries, such as the U.K. and Italy, reported a rise in preterm birthrates of 2% and 22%, respectively.
Researchers also noted that a comparison of preterm births before and after COVID-19 should take into account a variety of factors unique to the pandemic.
“While methodological challenges have hindered robust conclusions on whether lockdowns led to reductions in preterm births, there were undoubtedly unprecedented health, social and economic impacts that occurred as part of lockdowns that could potentially lead to reductions in preterm birth rates,” the analysis said. “The most well-established cause of spontaneous preterm birth is infection, and it is plausible that an immediate and substantial reduction in circulating infections during lockdown, due to reductions in social interaction and increased hygiene measures, could directly influence preterm birth rates.”
That’s one of the reasons the researchers focused on entire countries, or large sections of countries, rather than single hospitals or hospital systems, according to the study.
“We considered data sources as population-based if they captured more than 90% of births in the region or country, and non-population-based if coverage was ≤90%,” the study states.
Meghan Azad, Ph.D., an associate professor of pediatrics and child health at the University of Manitoba and one of the study’s leaders, told The New York Times that the genesis of the meta-analysis sprang from her reaction to an Irish study showing preterm births at one hospital in that country dropped by three-quarters or more. That sparked interest from other experts.
She told the newspaper that “it was this kind of crazy time. A bunch of researchers had a lot of time on their hands, because their projects were slowed down or their conferences were canceled.”
Azad also told the NYT that the meta-analysis gathered data in “a unique natural experiment, where the whole world experienced this pretty drastic lockdown at the same time. So it was a neat opportunity to look at what that might mean for maternal-child health.”