(CNN) The number of births in the United States fell by 4% last year, according to a new report from the US Centers for Disease Control and Prevention, and the pandemic may have presented the "perfect storm" for accelerated declines.
It's "the largest annual decline in the number of births since 1973," CDC researchers wrote in their report.
Births had been falling by about 2% a year already, but 2020 brought a greater decline, the CDC's National Center for Health Statistics reported.
CDC researchers counted 3.6 million births in 2020, based on provisional data. That's a decrease from about 3.75 million births in 2019 and 3.8 million births in 2018.
In the first half of 2020, births were down 2% and the number of births fell even more in the second half of 2020, with births down 4% in July, 7% in August, 4% in September, 6% in October and November, and 8% in December, the researchers found.
The coronavirus pandemic paired with an ongoing decline in US births, has presented the "perfect storm" for an accelerated decrease in the number of babies born, said Dr. Rahul Gupta, chief medical and health officer for the maternal and infant health nonprofit March of Dimes.
"We already have a maternal and infant health crisis in our country. We already have disproportionality in terms of racial disparities," Gupta, who was not involved in the new CDC report, told CNN.
"So, what this particular report points to is something we should take really seriously, which is: Is this decline going to have demographic impacts in the future? And that there will be both impacts in terms of workforce, in terms of economy, in terms of diversity, and population?" Gupta asked. "And obviously what happened in 2020, it will probably happen again at least in 2021."
The number of births declined for all states and Washington, DC, in the second half of last year compared with the same period in 2019.
The states with the largest declines in births for the second half of 2020 were: New Mexico, New York, California, Hawaii, and West Virginia. Declines were not seen as significant in seven states: Idaho, Maine, New Hampshire, North Dakota, Rhode Island, Vermont, and Wyoming.
The researchers also found some racial disparities. From 2019 to 2020, declines in the numbers of births each month were greater among women of color compared with White women.
"Evaluation of trends in births by month will continue to determine whether these declines continued into 2021 or were unique to 2020 during the time of the initial COVID-19 pandemic," the researchers wrote.