Infant mortality rates have increased in US states which have enacted abortion bans following the landmark ruling overturning the nationwide right for women to access the procedure, a new study has found.

The findings showed the highest mortality occurred among infants who were Black, lived in Southern states or had fetal birth defects.

Two studies, published Feb. 13 in JAMA, show that states that enforced complete or near-total abortion bans after six weeks of pregnancy saw a 6% overall rise in infant death rates. That added up to 478 more infant deaths than expected based on previous trends.

Overall, infant mortality was about four times higher among births linked to abortion bans than it was in the general population, said Dr. Suzanne O. Bell, lead author of the fertility study and researcher at the Johns Hopkins Bloomberg School of Public Health.