New research confirms what has been suspected for some time: women who suffer from morning sickness in the first trimester are less likely to miscarry.
In a study of over 2,000 pregnant women, those who had no symptoms of morning sickness in the first trimester were 3.2 times as likely to miscarry as the women who did have morning sickness.For older women the correlation was even more pronounced: miscarriage risk went up nearly 12-fold for women 35 and older with no morning sickness.
But women who don’t have morning sickness during their first trimester shouldn’t worry, reassures Dr. Ronna L. Chan, one of the study’s authors. “Not all pregnant women who go on to have successful pregnancies experience nausea and vomiting early on or at all. In addition, pregnancy symptoms can vary from one pregnancy to the next, even for the same woman.”
Researchers don’t know precisely why this is so but it could be the sharp rise in pregnancy hormones that are associated with both morning sickness and a healthy pregnancy. The main theory for why so many women are at least vaguely repulsed by lots of things in early pregnancy—if not downright vomiting—is that this is a protective mechanism, keeping women away from potentially harmful foods and toxins during the early weeks of crucial embryonic and fetal development.
After the first trimester, the placenta takes over more of the hormone production so mom is not as affected—this tends to coincide with an easing up for morning sickness and exhaustion. In this study, 89% of the women studied experienced some level of first trimester morning sickness, 53 % had actual vomiting, and 11% of the women miscarried before 20 weeks.