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Why morning sickness during pregnancy may be a good sign

Last Updated Sep 26, 2016 5:35 PM EDT

While experiencing nausea and vomiting during pregnancy is certainly unpleasant, it might very well be a sign that things are progressing smoothly.

According to a new study published in JAMA Internal Medicine, these symptoms – commonly referred to as morning sickness, though it can occur at any time of day – may be associated with a reduced risk of pregnancy loss.

“Nausea and vomiting can take a toll on a woman’s body, especially after the emotional time period of finding out you’re pregnant,” study author Stefanie N. Hinkle, Ph.D., a staff scientist at the Eunice Kennedy Shriver National Institute of Child Health and Human Development, told CBS News. “But our findings are really reassuring to women who are experiencing and suffering from these symptoms that their risk for pregnancy loss is greatly reduced. It’s helping to tell them that they have a healthy pregnancy and that this is a good thing.”

For the study, the researchers followed about 800 women whose pregnancies were confirmed by urine tests. The participants tracked their nausea and vomiting symptoms in pregnancy diaries and questionnaires. By the end of the study, 188 pregnancies (about 24 percent) ended in miscarriage.

After being pregnant for two weeks, nearly 18 percent of women reported nausea without vomiting and about 3 percent reported nausea with vomiting. Those numbers jumped to 57 percent and 27 percent, respectively, by the eighth week of pregnancy.

When the researchers crunched the numbers, they found that nausea or a combination of nausea and vomiting were associated with a 50 percent to 75 percent reduction in the risk of pregnancy loss in women with one or two prior pregnancy losses.

The findings reaffirm previous research with similar results. While the underlying mechanism for the connection is unknown, the researchers ruled out a few theories.

“There have been some hypotheses that women may change their lifestyle habits in response to feeling nauseous,” Hinkle explained. “So sort of an evolutionary instinct that could help prevent risky behaviors that have been linked to an increase risk of pregnancy loss like smoking or alcohol intake.”

However, the researchers ruled out these factors by controlling for them in their analysis, along with other lifestyle factors like caffeine and stress, which were recorded along with the morning sickness symptoms.

Hinkle said hormonal mechanisms might be at play but further research is needed to understand the underlying cause.

“The benefit of this study is that now we can actually tell patients that there’s evidence for this, that they’re not feeling miserable for no good reason. It actually demonstrates the pregnancy is progressing,” Dr. Leena Nathan, an OB/GYN in Westlake Village, California, told CBS News. “It’s a really important step forward, just so we can understand more about pregnancy – especially early pregnancy, which is when people are most anxious.”

In an accompanying editorial, Dr. Siripanth Nippita and Laura E. Dodge, Sc.D., MPH of the Beth Israel Deaconess Medical Center in Boston note that although the findings suggest nausea and vomiting have protective benefits, women should not be afraid to speak to their doctor about it if it is negatively impacting their lives.

“Although such a designation may provide reassurance to some women, they should not be discouraged from seeking treatment for a condition that can have a considerable negative effect on their quality of life,” they write.

Additionally, Hinkle said that women who do not experience nausea and vomiting during pregnancy should not feel alarmed. “Not all pregnancies are the same,” she said. “Everyone’s individual experience is different so just because you don’t have symptoms does not mean that you’re going to go on to have a loss.”

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    Ashley Welch covers health and wellness for CBSNews.com