The Number of Triplets Born in the U.S. Drops by 40%

Women are having fewer triplets than in the past, according to a new federal study looking at the rate of multiple births over time. Experts have been concerned over spikes in women having triplets—thought to be due to women getting pregnant later and the use of fertility enhancement technologies.

Having triplets or what experts call “higher-order births” (more than three babies) can take a toll on the woman having them, which is why, when the rate increased four-fold beginning in the 1980s, doctors were concerned. Since 1998, that number has gone down, and a new report from the National Center for Health Statistics released Thursday shows it dropped 41% from 1998 to 2014. “Triplet and higher-order multiple births continue to be at higher risk of poor outcome,” the study authors write, adding that triplets are less likely to survive their first year compared to single babies. “And those who did survive were more likely to suffer longterm morbidities.”

So what’s changed? The trend of women becoming mothers later has remained consistent throughout the study period. What’s different, the study authors note, are improvements in assisted reproductive technologies (ART) to help women conceive.

“There’s been a gradual shift in practices, especially in In Vitro Fertilization (IVF) centers, where there’s an emphasis on high pregnancy rates with fewer embryos and lower multiple births,” says Dr. Bradley Van Voorhis, the president of the Society for Assisted Reproductive Technology (SART). “There’s a substantial reduction in the number of embryos transferred due to advances in embryo selection and transfer.” Van Voorhis was not involved in the study.

The drop was not steady across all demographics. For non-Hispanic white women, high-order births are down 46% compared to 15% among Hispanic women. The rate appears to be unchanged for non-Hispanic black women. One possible reason is that women in those demographics are less like to have IVF procedures.

“This is a relatively new field and rapid advances have been made,” says Van Voorhis.