This spring, when countries around the world told people to stay home to curb the spread of the coronavirus, doctors in neonatal intensive care units noticed something strange: premature births were falling, in some cases dramatically. .
It started with doctors in Ireland and Denmark. Each team, unaware of the other’s work, reduced the numbers in their own region or country and found that during the blocks, premature births, especially the earliest and most dangerous cases, had plummeted. When they shared their findings, they heard similar anecdotal reports from other countries.
They don’t know what caused the drop in preterm births, and they can only speculate on the blocking factors that could have contributed. But additional research could help doctors, scientists, and expectant parents understand the causes of premature labor and ways to prevent it, which until now have been elusive. Their studies are not yet peer-reviewed, and have been published only on prepress servers. In some cases, the changes amounted to just a few babies missing from the hospital. But they represented significant reductions from the norm, and some experts in preterm labor think the research warrants further investigation.
“These results are compelling,” said Dr. Denise Jamieson, an obstetrician at Emory University School of Medicine in Atlanta.
About one in 10 American babies is born early. Pregnancy generally lasts about 40 weeks, and any delivery before 37 weeks is considered premature. The costs for children and their families, financially, emotionally, and in the long term, can be great. According to the Centers for Disease Control and Prevention, babies born prematurely, especially before 32 weeks, are at increased risk for vision and hearing problems, cerebral palsy and death.
The best way to avoid these costs would be to prevent preterm birth in the first place, said Dr. Roy Philip, a neonatologist at the University of Limerick Maternity Hospital in Ireland.
Dr. Philip had been on vacation abroad when his country entered the blockade on March 12, and he noticed something unusual when he returned to work in late March. He asked why there had been no requests while he was away for the breast-milk fortifier that doctors feed the hospital’s smallest premature babies. Hospital staff said it had not been necessary because none of these babies had been born in the entire month.
Intrigued, Dr. Philip and colleagues compared hospital births so far in 2020 with births between January and April in every year since 2001, more than 30,000 in total. They looked at birth weight, a useful indicator for very preterm delivery.
“Initially I thought, ‘There is something wrong with the numbers.'” Dr. Philip said.
Over the past two decades, babies under 3.3 pounds, classified as very low birth weight, accounted for approximately eight out of every thousand live births in the hospital, which serves a region of 473,000 people. In 2020, the rate was about a quarter of that. Smaller babies, those who weigh less than 2.2 pounds and are considered extremely low birth weight, generally account for three per thousand births. At least a few should have been born that spring, but there were none.
The study period was until the end of April. In late June, with the decline in national closure, Dr. Philip said there were still very few premature babies born in his hospital. In two decades, he said, he had never seen anything like this.
While the Irish team was researching their data, researchers in Denmark were doing the same, fueled by curiosity about a “nearly empty” NICU. Dr. Michael Christiansen of the Statens Serum Institut in Copenhagen and colleagues used newborn screening data to compare births across the country during the strictest period of confinement, March 12-April 14, with births during the same period in the previous five years. The data set included more than 31,000 babies.
The researchers found that during the shutdown, the rate of babies born before 28 weeks had dropped a staggering 90 percent.
Anecdotes from doctors in other hospitals around the world suggest that the phenomenon may have been widespread, although not universal.
Dr. Belal Alshaikh, a neonatologist at the University of Calgary in Alberta, said preterm births in Calgary fell by almost half during the shutdown. The change was widespread, although it seemed more pronounced in the first babies, he said.
At the Erasmus Medical Center in Rotterdam, The Netherlands, Dr. Irwin Reiss, a neonatologist, saw a smaller decrease in preterm births.
At Mercy Hospital for Women outside Melbourne, Australia, there were so few premature babies that administrators asked the hospital’s director of pediatrics, Dr. Dan Casalaz, to find out what was happening.
In the United States, Dr. Stephen Patrick, a neonatologist at Vanderbilt Children’s Hospital in Nashville, estimated that there were about 20 percent fewer babies in the NICU than usual in March. Although some term full-term babies would stay in the NICU, Dr. Patrick said premature babies generally made up the majority of patients, and neglect seemed to have been driven by missing premature babies.
When Dr. Patrick shared his observation on Twitter, some American doctors shared similar stories. Others said that their NICUs were as busy as ever. Some groups in other countries have said they also did not see a change.
If the blocks prevented preterm births in certain places but not others, that information could help reveal the causes of preterm birth. The researchers speculated on potential factors.
You could rest. By staying home, some pregnant women may have experienced less stress from work and commuting, slept more and received more support from their families, the researchers said.
Women who stay home could also have avoided infections in general, not just the new coronavirus. Some viruses, like the flu, can increase the chance of premature delivery.
Air pollution, which has been linked to some premature births, also decreased during blockades as cars stayed off the roads.
Dr. Jamieson said the observations were surprising because she would have expected to see more premature births during the stress of the pandemic, not less.
“It seems like we’ve experienced tremendous stress in the United States because of Covid,” he said.
But all pregnant women may not have experienced blockages in the same way, she said, since different countries have different social safety nets overall, and the stress of unemployment and financial insecurity may have affected communities unevenly.
Some subsequent preterm births could also have been prevented during blocks simply because doctors weren’t inducing mothers for reasons like high blood pressure, Dr. Jamieson said. But that would not explain a change in very early preterm births, as the Danish and Irish authors found.
“The causes of preterm birth have been elusive for decades, and ways to prevent preterm births have been unsuccessful,” said Dr. Jamieson. According to the CDC, premature births in the United States increased in 2018 for the fourth consecutive year. White women had about a 9 percent risk of preterm delivery in 2018, while the risk for African American women was 14 percent.
If the trends in the data are confirmed, the pandemic and blockages could be something like a natural experiment that could help researchers understand why preterm labor occurs and how to avoid it. Maybe a maternity leave should start before the mother’s due date, for example.
Danish and Irish researchers have teamed up and are forming an international group of collaborators to study how Covid’s blockages affected preterm births.
“For years, nothing has progressed in this important area,” said Dr. Christiansen, “and it appears that a virus attack was needed to help us get on track.”
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