Preterm births dropped in 2022. Now study says COVID vaccines are to thank for change
The COVID-19 pandemic posed a particular risk for pregnant people, but a new study says the vaccines that followed may have prevented thousands of premature births.
In the early days of the pandemic, hospitals around the country noticed a spike in the cases of babies born earlier than expected when their mothers had been infected with COVID-19, a study published on Nov. 27 in the Proceedings of the National Academy of Sciences said.
Researchers from the University of California, Berkeley, analyzed statewide data of a representative population of California to see how this trend played out in the years that followed.
They found starting in 2020, there was a 15% increase in the probability a baby would be born preterm if the mother was infected with COVID-19 at the time of delivery, according to the study.
From July 2020 to the end of 2020, preterm births increased more than five points in the researchers’ models, representing a 78% increase in the chance a baby would be born preterm to a COVID-19 infected mother, according to the Berkeley study.
The values were adjusted to include different socioeconomic statuses and pre-existing risk factors in the pregnant people included in the data, the researchers said, factors that could place limits on the conclusions.
The numbers continued to fluctuate during 2021, with a change of anywhere between 2 and 4 percentage points, peaking in fall 2021 when the Delta variant was driving the wave of cases, the researchers said in the Berkeley study.
But the trend didn’t continue.
“The impact of COVID-19 infection disappears in 2022,” the researchers wrote. “No indication or change is observed thereafter, even during the surge in Omicron infections in the summer of 2022.”
What do researchers believe caused the change?
“The decline and then disappearance of an adverse impact of COVID-19 on preterm birth in 2022 occur in the context of growing infection-based immunity, the potentially reduced virulence of the Omicron variant, increased uptake of COVID-19 vaccination, and growing access to therapeutic management of the COVID-19 infection,” the researchers said.
By December 2022, nearly 70% of pregnant people had received at least two doses of the vaccine, the study said, meaning many got their first dose in late 2021 or in early 2022.
“The harmful impact of COVID-19 infection disappeared almost a year earlier in zip codes with high vaccination rates, suggesting that vaccines might have prevented thousands of preterm births,” according to the study.
COVID-19 vaccinations were recommended for pregnant people beginning in April 2021, and in the months that followed, preterm births decreased.
“This is a profound change and represents thousands of averted preterm birth and accompanying complications for those children and their families,” the researchers said.
Time will tell if this trend continues as COVID-19 enters its fourth year, the researchers say, particularly as new strains emerge.
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