A new meta-study finds that women who want to become pregnant should avoid light at night, reports the Huffington Post.

Darkness is important for optimum reproductive health in women, and for protecting the developing fetus, said study researcher Russel J. Reiter, a professor of cellular biology at the University of Texas Health Science Center in San Antonio.

In a review of studies published online July 1 in the journal Fertility and Sterility, Reiter and his colleagues evaluated previously published research, and summarized the role of melatonin levels and circadian rhythms on successful reproduction in females.