'Morning sickness' associated with a reduced risk for pregnancy loss

Women who experience nausea with or without vomiting during pregnancy had a lower risk of pregnancy loss, according to data published in JAMA Internal Medicine.

Stefanie N. Hinkle, PhD, from the Eunice Kennedy Shriver National Institute of Child Health and Human Development at the NIH, and colleagues noted the protective association may reassure women who are dealing with symptoms of morning sickness.

“Nausea with or without vomiting is reported by as many as 80% of women during pregnancy and can have a substantial negative effect on quality of life,” Hinkle and colleagues wrote. “Although speculation commonly suggests that nausea is a good sign and indicative of healthy pregnancy, evidence supporting this assertion is limited.”

The researchers conducted a secondary analysis of the randomized clinical trial, Effects of Aspirin in Gestation and Reproduction, which included 797 women who had a human chorionic gonadotropin (hCG)-confirmed pregnancy. Participants completed preconception and pregnancy diaries and questionnaires regarding their symptoms.

Hinkle and colleagues reported 188 pregnancies (23.6%) ended in loss.

Results showed 73 of 409 women reported nausea without vomiting and 11 reported nausea with vomiting by their second week of gestation. By their eighth week, 254 women reported nausea without vomiting and 118 reported nausea with vomiting.

Both nausea without vomiting (hazard ratio [HR] = 0.44; 95% confidence interval [CI], 0.26-0.74) and nausea with vomiting (HR = 0.2; 95% CI, 0.09-0.44) were linked to a lower risk of clinical pregnancy loss.

“Among women with one or two prior pregnancy losses, nausea and nausea with vomiting during pregnancy were associated with a 50% to 75% reduction in the risk for pregnancy loss,” Hinkle and colleagues concluded. “Nausea and vomiting symptoms were common early in pregnancy. These findings overcome prior analytic and design limitations and represent the most definitive data available, to our knowledge, indicating the protective association of nausea and vomiting in early pregnancy on the risk for pregnancy loss and thus, may provide reassurance to women experiencing these difficult symptoms in pregnancy.”

Siripanth Nippita, MD, MS, and Laura E. Dodge, ScD, MPH, both from the Beth Israel Deaconess Medical Center and Harvard Medical School, discussed various theories as to why morning sickness may contribute to a lower risk of pregnancy loss. Those hypotheses include a lower caloric intake, which may benefit fetal development and placental growth.

“[A] third hypothesis takes the opposite approach and considers nausea and vomiting a consequence of a normally progressing pregnancy,” Nippita and Dodge said. “Nausea and vomiting in pregnancy usually begins in the late first trimester, when the risk for pregnancy loss has already decreased relative to earlier in the first trimester and can be seen as a marker of rising hCG and progesterone levels that are consistent with a viable pregnancy.”

They wrote that Hinkle and colleagues research adds value to an existing body of research.

“The investigators were able to compare the incidence of nausea and vomiting symptoms among women who experienced an early pregnancy loss with those whose pregnancies continued,” Nippita and Dodge wrote. “By collecting daily urine samples, it was possible to identify all pregnancies early in gestation and thus definitively quantify the losses that occurred around the time of implantation in addition to those that occurred after ultrasonography.”

However, they warned physicians about how they communicate the roles nausea and vomiting in pregnancy loss to patients.

“As common as nausea and vomiting are in the first trimester, researchers and clinicians should be cautious about deeming it to have a protective effect against pregnancy loss. 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.”

Nippita and Dodge wrote that preconception cohort studies can help physicians and patients understand the mechanisms behind nausea and vomiting during pregnancy.

“Findings from these studies would be of interest to women trying to conceive and the clinicians who care for them, and they may be of particular interest to women undergoing fertility treatment,” they wrote. “The widespread availability of sensitive urine hCG tests coupled with real-time electronic data capture using mobile phone apps or similar technology has the potential to improve data quality and eliminate recall bias.” – by Chelsea Frajerman Pardes