On Oct. 6, 2021, a study by researchers at the National Institutes of Health (NIH) found that episodes of maternal stress or depression during pregnancy are associated with chemical modifications to placental genes, according to a study published in Epigenomics.

The modifications involve DNA methylation – binding of compounds known as methyl groups to DNA – which can alter a gene’s activity. Some of the methylation changes associated with maternal depression occurred near genes involved in brain development, suggesting that maternal depression in pregnancy could have long-term implications for the mental development of the child.