Objective: The experience of women was sought about nausea and vomiting, its relation to olfaction, its occurrence among pregnant women with anosmia, and the potential association of hyperemesis gravidarum and migraine headache.
Methods: We performed a community-based study with a physician/patient-directed questionnaire, and a retrospective analysis of hospital records.
Results: Nearly all women (n = 163 parous women) experience nausea (98%) and vomiting (97%). The highest frequency causes of nausea and vomiting were "food poisoning" (65%), "flu" (58%), pregnancy (54%), and offensive odors (52%); vomiting occurred as frequently as nausea for the first 2 causes, and one half as often for the latter causes. Most women reported that the pain experienced during vomiting exceeded that of parturition. Among 9 women with hypogonadotropic anosmia with advanced reproductive technology-induced pregnancies, 2 experienced nausea and vomiting, one from "food poisoning." Among 37 women with migraine headache, 10 (27%) had experienced hyperemesis gravidarum, and among 16 who experienced hyperemesis gravidarum, 5 (37%) had migraine headaches.
Conclusions: The frequency of nausea and vomiting, caused most often by nonpregnancy-related triggers, is high among women. In a small sample of women with congenital anosmia, nausea and vomiting of pregnancy occurred in only 1 pregnancy, suggesting that olfaction is a highly selected trigger for nausea and vomiting of pregnancy. The shared nausea and vomiting experience of hyperemesis gravidarum and migraine headache among women suggests a common mechanism, possibly based on allelic variations within the DRD2 (dopaminergic receptor) gene. Because olfactory receptors, odor types, and MHC antigens are closely integrated, and because olfactory stimuli often incite episodes of pregnancy, nausea, and vomiting, hyperemesis gravidarum, and migraine headache, these genes and their products invite further scrutiny. The pregnancy-conserving effect of PNV and the MHC antigen overlap in couples with recurrent abortion are important clues possibly relating olfaction, MHC antigens, and reproductive success or failure.