The birth rate in the United States last year fell to its lowest rate in more than three decades, according to a federal report released Wednesday.

Data from the Centers for Disease Control and Prevention show 3.79 million babies were born in the U.S. in 2018, a 2% drop from the previous year and the lowest total since 1986.It was the fourth straight year births declined in the United States.

The fertility rate also dropped 2% to 1.7 births per woman, a record low. This indicates the current generation of women between the ages of 15 to 44 is not having enough babies to replace itself.

Births among teenagers fell 8%, but birth rates among women in their late 30s and early 40s were slightly higher, the only groups to experience an increase.

Last year’s birth rate decline was the 10th in the last 11 years, since it peaked in 2007 just before the Great Recession. 

Years of birth rate declines are unusual under a robust economy and it remains unclear whether U.S. women are delaying motherhood or skipping it altogether. 

Many researchers predict U.S. worker shortages in the coming years if the trends continue.