Deciphering Nausea and Vomiting of Pregnancy

abstract & commentary

Source: Lacroix R, et al. Nausea and vomiting during pregnancy: A prospective study of its frequency, intensity, and patterns of change. Am J Obstet Gynecol 2000;182:931-937.

This prospective study was undertaken to provide a detailed description of the natural patterns of nausea and vomiting during normal pregnancy. The study group consisted of 160 pregnant women who provided daily recordings of the frequency, duration, and severity of nausea and vomiting. The McGill Nausea Questionnaire was used to rate the intensity of the nausea both quantitatively and qualitatively. This questionnaire has been validated in previous work done by one of the authors in patients with nausea and vomiting from chemotherapy. Of 200 potential subjects, five refused to participate, 15 did not complete the questionnaire, and 20 participants miscarried and were excluded. Women who were admitted to the hospital for hyperemesis gravidarum were not included in the study.

Of the 160 subjects, 118 (74%; 95% CI, 66%-80%) reported pregnancy-associated nausea and 60 (38%; 95% CI, 30%-45%) reported vomiting. The mean gestational age at onset of nausea was 5.7 weeks, and nausea lasted a mean of 35 days (range, 1-114 days). Although 50% of women with nausea reported resolution by 14 weeks, it was not until week 22 that nausea had resolved in 90% of the women. Week 11 of gestation was the week in which the highest proportion of women (40%) had nausea and was also the peak week for vomiting. The mean score on the overall nausea index during this week was 1.85 (on a 0-5 scale; 0 is no nausea). Nausea was limited to mornings alone in only 1.8% (95% CI, 0%-7%) of affected women, and lasted all day in 80% (95% CI, 71%-87%).

Age, height, and weight of the subjects during the first trimester were not predictive of nausea and vomiting during pregnancy. Women with less education were significantly more likely to report nausea and vomiting and had higher intensity scores. Women with nausea during a previous pregnancy were significantly more likely to report nausea and vomiting during the index pregnancy. Whether the mothers of the study subjects had experienced nausea during pregnancy was unrelated to the study subjects’ current experience. The occurrence of nausea and vomiting did not predict the gender or birth weight of the child.


Surprisingly little research has been done in this area. Therefore, a study as simple as defining the natural history of nausea and vomiting in pregnancy is important.

It should be noted that because this study excluded patients who required admission to the hospital, the data do not include those patients with true hyperemesis gravidarum. The first apparent myth of pregnancy (written in major textbooks) is that the nausea and vomiting of pregnancy will disappear by the end of the first trimester. However, the data from this study and others show that the prevalence is greatest at 11 weeks gestation and the severity in those affected peaks at 11-13 weeks. Only half the women with nausea and vomiting were completely relieved by 14 weeks, and it was not until week 22 that nausea had resolved in 90% of affected women. The second apparent myth of pregnancy (and the origin of the misleading term "morning sickness") is that nausea and vomiting are worst on awakening and usually will not outlast the morning. This study found that less than 2% of women had nausea confined to just the mornings, while nausea and vomiting lasted all day long for 80% of those affected. Given that other studies have demonstrated similar results, it may be time to rewrite the textbooks. More importantly, as physicians, we need to inform our patients about the natural history of nausea and vomiting during pregnancy so they can have realistic expectations about this difficult syndrome. By doing this, both patient and doctor may avoid unnecessary frustration when the symptoms persist.