Now, there's more science to support the idea.
Writing in the journal JAMA Internal Medicine, the experts, from the National Institutes of Health in Maryland, in the U.S., concluded: "Our study confirms prior research that nausea and vomiting appear to be more than a sign of still being pregnant and instead may be associated with a lower risk for pregnancy loss".
As many as four out of five women report nausea or vomiting during pregnancy, the researchers said in background notes.
All of the women in the study were trying to conceive during the study period, and almost 800 of them became pregnant, according to the researchers.
About 84 percent of the women reported nausea, with or without vomiting, by the time they were eight weeks pregnant. The women who reported experiencing nausea or nausea with vomiting by the 8th week of pregnancy - 57.3 percent and 26.6 percent respectively - were 50 to 75 percent less likely to have a pregnancy loss than those who hadn't experienced those symptoms.
Morning sickness afflicts most pregnant women, but new research has found it comes with a silver lining.
Younger moms, in general, tend to experience more frequent morning sickness. The NIH researchers controlled for these and other circumstances in their assessment, giving them a clearer picture that the association between morning sickness and reduced pregnancy loss is strong-without confounding factors getting in the way.
Among the women, 188 pregnancies (nearly 24 percent) ended in loss, the investigators found.
"As common as nausea and vomiting are in the first trimester of pregnancy, researchers and clinicians should be cautious about deeming it to have a protective effect against pregnancy loss", Dr. Siripanth Nippita, an OB/GYN at Beth Israel Deaconess Medical Center in Boston, and Laura Dodge, a staff scientist at the same institution, wrote in an editorial that was published alongside the study in JAMA Internal Medicine.
But it doesn't mean that expectant moms who aren't grappling with bouts of morning sickness should be anxious. The study had some other limitations, too. It is thought to be caused by pregnancy hormones, but it is unclear why some women get it worse than others.
"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. Scientists have suggested that pregnancy illness is a byproduct of rapid hormonal changes, especially the increase of human chorionic gonadotropin, or hCG.
The authors looked at data from all the women in the study who had a positive pregnancy test.
While experiencing nausea and vomiting during pregnancy is certainly unpleasant, it might very well be a sign that things are progressing smoothly.
Scientists are also unsure about whether there's an evolutionary reason for morning sickness to carry protective benefits. Women aged 25 and under were more likely to suffer nausea.
The researchers said morning sickness can "have a substantial negative effect on quality of life". But since their model accounted for smoking and drinking alcohol, it seems "the mechanism is likely not through avoidance of such substances". "However, it is important to emphasise that if a woman isn't suffering from nausea and vomiting, it doesn't mean she will miscarry".