At the start of the coronavirus lockdowns, some predicted that all the time Americans spent indoors with little to do would lead to a baby boom. It will be several months before definitive data is available, but evidence suggests that the COVID-19 pandemic will actually lead to a baby bust.

The combined influence of stress, economic uncertainty and fewer opportunities for people to meet could lead to as many as 500,000 fewer babies born in the U.S. in 2021, one study found. Any coronavirus baby bust would extend a trend...