According to researchers at The University of Texas Health Science Center at Houston, exposure in utero to a drug used to prevent miscarriage can lead to an increased risk of developing cancer.

The findings of the study were published in the American Journal of Obstetrics and Gynaecology. The drug, 17-OHPC, is a synthetic progestogen that was frequently used by women in the 1950s and 1960s and is still prescribed to women today to help prevent preterm birth. Progesterone helps the womb grow during pregnancy and prevents a woman from having early contractions that may lead to miscarriage.

"Children who were born to women who received the drug during pregnancy have double the rate of cancer across their lifetime compared to children born to women who did not take this drug," said Caitlin C. Murphy, PhD, MPH, lead author on the study and associate professor in the Department of Health Promotion and Behavioral Sciences at UTHealth School of Public Health in Houston.

"We have seen cancers like colorectal cancer, pancreatic cancer, thyroid cancer, and many others increasing in people born in and after the 1960s, and no one really knows why," Murphy added. Researchers reviewed data from the Kaiser Foundation Health Plan on women who received prenatal care between June 1959 and June 1967, and the California Cancer Registry, which traced cancer in offspring through 2019.

Out of more than 18,751 live births, researchers discovered 1,008 cancer diagnoses were made in offspring ages 0 to 58 years. Additionally, a total of 234 offspring were exposed to 17-OHPC during pregnancy. Offspring exposed in the womb had cancer detected in adulthood more than twice as often as offspring not exposed to the drug -- 65 per cent of cancers occurred in adults younger than 50.

"Our findings suggest taking this drug during pregnancy can disrupt early development, which may increase risk of cancer decades later," Murphy said. "With this drug, we are seeing the effects of a synthetic hormone. Things that happened to us in the womb, or exposures in utero, are important risk factors for developing cancer many decades after we're born," Murphy added.

A new randomised trial shows there is no benefit of taking 17-OHPC, and that it does not reduce the risk of preterm birth, according to Murphy. The US Food and Drug Administration proposed in October 2020 that this particular drug be withdrawn from the market.