With their large data set, the researchers compared early births in windows one to four months before and after the lockdown. Looking at the same windows in earlier years let them account for any other trends, such as seasonal changes in premature birth. No matter which windows they used, the researchers saw that premature births had dropped after March 9, when the government in the Netherlands began warning the public to take more hygiene measures and to stay home if they had symptoms or possible exposures to the virus. Within the next week, schools and workplaces began to close down…

One of those unanswered questions is about stillbirths. In the best-case scenario, the preemies that were missing from hospitals this spring were born as healthy full-term infants. But it’s possible that some of those missing preemies died, instead.

Stillbirths “might actually be the dark side of this,” Dr. Been said. Researchers couldn’t measure stillbirths in the Dutch data set, because only live infants undergo newborn screening. If most of the missing preemies were actually stillborn, Dr. Been said, there would have to have been a huge increase in stillbirths — maybe three times the usual number, conservatively. No one has reported such a change so far.