"Although the exact mechanism responsible for causing nausea and vomiting during pregnancy has yet to be pinpointed, it likely is a result of changing levels of ovarian and placental hormone production, which may include higher circulating levels of a hormone called human chorionic gonadotropin," said David Jaworowicz, Jr., first author, University at Buffalo. "In vitro studies have shown that this hormone possesses several activities that have potential protective effects against cancer cells.”

The analysis compared extensive data on pregnancy-related conditions from 1,001 women with primary breast cancer and 1,917 women without breast cancer matched to cases by age and race who served as controls.

The scientists tried to find associations between pregnancy-related events and characteristics, including pregnancy-induced hypertension, preeclampsia/eclampsia, gestational diabetes, high weight gain during pregnancy, and nausea and vomiting. These markers may serve as proxies for underlying hormonal changes and altered hormone levels in blood and tissue.

Jaworowicz noted that the presence or absence of these pregnancy-related conditions may indicate a different course or extent of hormone-regulated breast tissue proliferation and differentiation during pregnancy, but also may indicate distinct hormonal profiles that persist following pregnancy. Evidence from the current analysis did suggest that a lower risk of developing breast cancer observed with nausea and vomiting was stronger as the symptoms became more severe, or persisted longer into pregnancy.

"Pregnancy is a time of drastic physiological changes," he noted. "The rapidly changing anatomy of the breast makes it more susceptible to errors in DNA replication or repair, which may translate into breast cancer,” Jaworowicz explained.

MEDICA.de; Source: University at Buffalo