Lack of premature births surprises doctors

This spring, as countries around the world told people to stay home to slow the spread of the coronavirus, doctors in neonatal intensive care units were noticing something strange: Premature births were falling, in some cases drastically.

It started with doctors in Ireland and Denmark. Each team, unaware of the other’s work, crunched the numbers from its own region or country and found that during the lockdowns, premature births — especially the earliest, 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 premature births and can only speculate as to the factors in lockdown that might have contributed. But further research might help doctors, scientists and parents to be understand the causes of premature birth and ways to prevent it, which have been elusive until now.

Their studies are not yet peerreviewed and have been posted only on preprint servers. In some cases, the changes amounted to only a few less babies per hospital. But they represented significant reductions from the norm, and some experts in premature birth think the research is worthy of additional investigation.

“These results are compelling,” said Dr. Denise Jamieson, an obstetrician at Emory University’s School of Medicine in Atlanta.

About 1 in 10 U.S. babies is born early. Pregnancy usually lasts about 40 weeks, and any delivery before 37 weeks is considered preterm. The costs to children and their families — financially, emotionally and in long-term health effects — can be great. According to the Centers for Disease Control and Prevention, babies born premature, especially before 32 weeks, are at higher risk of vision and hearing problems, cerebral palsy and death.

The best way to avoid these costs would be to prevent early births in the first place, said Dr. Roy Philip, a neonatologist at University Maternity Hospital Limerick in Ireland.

Philip noticed something unusual in late March. He asked why there had been no orders while he was gone earlier for the breast milk-based fortifier that doctors feed to the hospital’s tiniest preemies. The hospital’s staff said that there had been no need because none of these babies had been born all month.

Over the past two decades, babies under 3.3 pounds, classified as very low birth weight, accounted for about 8 of every 1,000 live births in the hospital. In 2020, the rate was about one-quarter of that. The very tiniest infants, those under 2.2 pounds and considered extremely low birth weight, usually make up 3 per 1,000 births. There should have been at least a few born that spring — but there had been none.

The study period went through the end of April. By the end of June, with the national lockdown easing, Philip said there had still been very few early preemies born in his hospital.

Danish researchers found that during the lockdown, the rate of babies born before 28 weeks had dropped by a startling 90 percent in their nation.

Anecdotes from doctors at other hospitals around the world suggest the phenomenon may have been widespread, though not universal.

In the U.S., Dr. Stephen Patrick, a neonatologist at Vanderbilt Children’s Hospital in Nashville, Tenn., estimated that there were about 20 percent fewer NICU babies than usual in March. Although some sick full-term babies would stay in the NICU, Patrick said preterm babies usually made up most of the patients, and the drop-off seemed to have been driven by fewer preemies.

When Patrick shared his observation on Twitter, some U.S. doctors shared similar stories. Others said their NICUs were as busy as ever.

If lockdowns prevented early births in certain places but not others, that information could help reveal causes of premature birth. The

Researchers speculated about potential factors. One could be rest. By staying home, some pregnant women may have experienced less stress from work and commuting, gotten more sleep and received more support from their families, the researchers said.

Women staying at home also could have avoided infections in general, not just the new coronavirus. Some viruses, such as influenza, can raise the odds of premature birth.

Air pollution, which has been linked to some early births, has also dropped during lockdowns as cars stayed off the roads.