Latina immigrants in New York City have seen a spike in premature births – an increase that researchers with the city’s health department say may be tied to the shock win by Donald Trump in the 2016 presidential election.

The study released Wednesday by the health department and Harvard’s TH Chan School of Public Health compared births in the city in the months before Trump won the Republican presidential nomination, from September 2015 through July 2016, with births in the months after he was inaugurated, from January to August 2017.

There was no change in babies born prematurely – or before 37 weeks of pregnancy – among American-born women. But among foreign-born women, the rate increased from 6.7% to 7%.

The biggest jump was among immigrant Latinas, especially those born in Mexico and Central America, whose rates rose from 7.3% to 8.4%.

The study is the first to look at the effect of the US presidential campaign and election on premature births.

Severe stress – including social and political stress tied to hostile rhetoric and public policy – can contribute to women giving birth early, the researchers said. They cite the spike in hate crimes in the aftermath of the election as another source of stress. Attacks on Muslims in the US increased sharply and hostility towards Latinxs rose, too.

“This analysis highlights how the stress caused by racism and discrimination may induce preterm births, which are extremely harmful to both mothers and babies,” said acting city health commissioner Dr Oxiris Barbot.

During the period studied, the overall rate of premature births in the city increased from 7% to 7.3%.

Black women had the highest rate of preterm birth, at 10.3%, but rates did not change for black or white women.

“The results suggest changes in the severity of sociopolitical stressors may be adversely impacting health of the targeted populations and these health impacts warrant public health monitoring,” the study said.