1. Compared to women who had pregnancies conceived from in vitro fertilization (IVF), women who conceived from frozen embryo transfer (FET) cycles had more prevalent and severe nausea and vomiting.
2. Estrogen and progesterone may play a role in nausea and vomiting, however those in the FET group had lower hormone levels than those in the IVF group, suggesting various other factors involved.
Evidence Rating Level: 2 (Good)
70-80% of pregnant women are affected by nausea and vomiting, with the mechanisms being unknown but multifactorial in nature, including the role estrogen and progesterone. Estrogen causes downstream effects such as delaying of gastric emptying, and previous studies have found that women with hyperemesis of pregnancy have higher levels of estradiol. Progesterone can also reduce smooth muscle contraction, resulting in decreased gastric emptying. The additive effects of both hormones are demonstrated by increased gastric slow wave rhythm. Pregnancies can be achieved via assisted reproduction in two ways, either through stimulated in vitro fertilization (IVF) or frozen embryo transfers (FET). In IVF cycles, the ovaries are stimulated resulting in estradiol levels higher than FET cycles, whereas FET cycles have hormone levels are closer to physiological ranges. To further characterize whether or not IVF or FET pregnant women would have different outcomes on nausea and vomiting, 360 women were recruited in this prospective study, with 171 undergoing IVF and 189 undergoing FET. These women were carrying singleton pregnancies with no previous gastric issues. The patients were screened between 6 and 12 weeks gestation and asked to fill out the modified Pregnancy Unique Quantification of Emesis and Nausea (PUQE) questionnaire. This index included the amount of time the subjects felt nauseated, how often they vomited and how often they retched or dry heaved. During weeks 11 and 12 of gestation, significantly more women felt nauseated in the FET group (p value = 0.032 for week 11 and p value = 0.046 for week 12). In weeks 7 and 8, significantly more women in the FET group had longer duration of nausea (p value = 0.044 for week 7 and p value = 0.030 for week 8) and during week 6, significantly more women in the FET group had more vomiting in a day. These results were not consistent with the initial hypothesis of higher hormone levels correlating with more nausea and vomiting, suggesting many other factors such as multiparity, levels of beta-human chorionic gonadotropin levels and age impacting nausea and vomiting of pregnancy. This study was limited in its potential for recall bias, as well as lack of measuring blood levels of hormones in the two groups. Further studies are needed to further investigate the relationship between hormone levels and nausea and vomiting as well as other factors that may contribute.
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