Early on in the pandemic, there were reports of lower levels of preterm births and low birth weight, but also some reports of no change. This study reports on the early US data now available for March through December 2020, comparing rates of preterm birth and low birth weight (which are of course correlated with each other) with prior years.
There was a statistically significant decline in both low birth weight and premature birth during this time period compared to previous years. The effect was much stronger for very early / very small babies. That is, there was a greater decline in babies born at <34 weeks or <1500g (3.3 lbs) than for those born only less early.
The decrease was not evenly distributed across the months. It turns out that early births are seasonal. They peak in the spring and are at their lowest rate in the late summer / early fall. So they are comparing with the predicted rate for each month. Some months the decrease was more dramatic than others. The fall decline in extra-small babies was especially dramatic in 2020, for example. If you look at overall preterm births, they were lower than expected for every month in this time period except June and August.
We don't really know what caused this decline. I thought maybe less exposure to other viruses like colds and flu. It is an interesting observation, and gives us at least one positive outcome from a dark year.
