Infant mortality increased along with births in most states with abortion bans in the first 18 months after the Supreme Court overturned Roe v. Wade, according to new research.

The findings, in two studies published Thursday in the journal JAMA, also suggest that abortion bans can have the most significant effects on people who are struggling economically or who are in other types of challenging circumstances, health policy experts said.

“The groups that are most likely to have children as a result of abortion bans are also individuals who are most likely, for a number of different reasons, to have higher rates of infant mortality,” said Alyssa Bilinski, a professor of health policy at Brown University, who was not involved in the research.

Overall, infant mortality was 6 percent higher than expected in states that implemented abortion bans, said Alison Gemmill, one of the researchers, who is a demographer and perinatal epidemiologist in the department of population, family and reproductive health at the Johns Hopkins Bloomberg School of Public Health. That number reflected increases in nine states, decreases in four and no change in one.

Dr. Gemmill said that among non-Hispanic Black infants, mortality was 11 percent higher after abortion bans were implemented than would have been expected. Also, there were more babies born with congenital birth defects, situations in which women have been able to terminate their pregnancies if not for abortion bans.

Overall, the researchers found that in the states that implemented near-total abortion bans or bans after six weeks’ gestation during that period, there were 478 more deaths of babies in their first year of life after the bans were implemented than would have been expected based on previous years’ data.