Post traumatic stress disorder (PTSD) is a risk factor for premature birth, research suggests.
A study of more than 800 women in the US also found a link with having a smaller baby.
Babies of women with the anxiety disorder, triggered by a harrowing event, weighed about half a pound less than usual.
Researchers at the University of Michigan, US, say PTSD needs to be taken into account in maternity care.
Nearly half of the women in the study were African American.
Lead researcher Julia Seng, Professor of Nursing at the University of Michigan, said: "An African American infant in Michigan is 70% more likely to be born prematurely than an infant of any other race.
"Therefore PTSD, which is treatable and affects African Americans more widely, may be an additional explanation for adverse perinatal outcomes.
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