Morning sickness is linked to a lower risk of miscarriage, according to research out Monday that suggests a woman's nausea and vomiting early in pregnancy may have protective effects for the fetus.
Between 50 and 80 percent of pregnant women report feeling nauseous or throwing up during their first trimester, said the findings in the Journal of the American Medical Association (JAMA) Internal Medicine.
The condition is often called "morning sickness," though it can affect women at all times of the day and night.
In a study of 797 women, nausea and nausea with vomiting were associated with a 50 percent to 75 percent reduction in the risk of pregnancy loss, said the report, led by Enrique Schisterman of the US National Institute of Child Health and Human Development.
The women had all had one or two prior pregnancy losses. They tracked their nausea symptoms in a diary, and their pregnancies were confirmed by urine tests.
Prior research has also suggested that nausea and vomiting are linked to a lower risk for pregnancy loss.
Some experts believe nausea may encourage a healthy pregnancy by leading women to eat less, thereby reducing the risk of exposing the fetus to toxins.
The reduction in food intake also appears to lower levels of circulating insulin and encourage growth of the placenta, research has shown.
The new study did not delve into reasons why nausea and vomiting may lower the risk of miscarriage.
An accompanying editorial in JAMA by Siripanth Nippita of Beth Israel Deaconess Medical Center and Laura Dodge of Harvard Medical School described its contribution to existing medical literature as "valuable for several reasons," including its large size and rigorous methods for comparing symptoms among women who experienced an early pregnancy loss with those whose pregnancies continued.
"Given these methodologic advantages over previous investigations, we hope that such studies can further deepen our understanding of the underlying causes of nausea and vomiting in pregnancy," they wrote.