During Coronavirus Lockdowns, Some Doctors Wondered: Where Are the Preemies?

About one 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.

Dr. Philip had been vacationing abroad when his country entered lockdown on March 12, and he noticed something unusual when he returned to work in late March. He asked why there had been no orders while he was gone 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.

Intrigued, Dr. Philip and his colleagues compared the hospital’s births so far in 2020 with births between January and April in every year since 2001 — more than 30,000 in all. They looked at birth weights, a useful proxy for very premature birth.

“Initially I thought, ‘There is some mistake in the numbers,’” Dr. Philip said.

Over the past two decades, babies under 3.3 pounds, classified as very low birth weight, accounted for about 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. The very tiniest infants, those under 2.2 pounds and considered extremely low birth weight, usually make up three per thousand births. There should have been at least a few born that spring — but there had been none.