Researchers examined data from nearly 1 600 women who gave birth in 2005. Some of the women worked full-time or part-time while pregnant, while others did not work during their pregnancy.
There were no differences in the rates of premature birth or low birth-weight babies between the women who worked or stayed at home while pregnant, the University of Minnesota investigators found.
However, known risk factors (such as being black) remained strongly associated with pre-term birth and low birth weight, according to the study published online recently in the journal Women's Health Issues.
Type of job important
"Prior research shows an association between certain job characteristics, such as strenuous physical labour and long work hours, and adverse birth outcomes, but often fails to disentangle a woman's employment choices from her birth outcomes, given that women who work during pregnancy - out of choice or out of need - are very different from those who do not," study leader Katy Backes Kozhimannil, of the division of health policy and management, said in a university news release.
The researchers said their findings show that the focus should not be on whether or not a woman works while she is pregnant, but rather on job characteristics, especially those that are known to increase the risk of pre-term birth and low birth weight.
"Our findings reiterate the importance of ongoing policy dialogue about the challenges faced by working mothers," Kozhimannil said.
Kozhimannil noted that the Pregnant Workers Fairness Act, currently under consideration in Congress, has prompted debate on how best to promote healthy pregnancies among working women.
The US National Library of Medicine has more about working