BackgroundNausea and vomiting during pregnancy (NVP) is considered to be associated with favorable fetal outcomes, such as a decreased risk for spontaneous abortion. However, the relationship between NVP and preterm births remains unknown. This study was conducted to evaluate the association between NVP and the risk of preterm births.MethodsThe dataset of a birth cohort study, the Japan Environment and Children’s Study (JECS), was retrospectively reviewed. Participants’ experience of NVP prior to 12 gestational weeks were evaluated by a questionnaire administered from 22 weeks of pregnancy to 1 month before delivery. NVP responses were elicited against four choices based on which the study population was divided into four subcohorts. Preterm birth was the main study outcome. Logistic regression analysis was used to quantify an association between NVP and risk of preterm birth.ResultsOf 96,056 women, 79,460 (82.7%) experienced some symptoms of NVP and 10,518 (10.9%) experienced severe NVP. Compared to those who did not experience NVP, women with severe NVP had lower odds for preterm birth [adjusted odds ratio (aOR) 0.84, 95% confidence interval (95% CI) 0.74–0.95]. An even lower OR was found among very preterm birth and extremely preterm birth (aOR 0.44, 95% CI 0.29–0.65).ConclusionAn inverse association exists between NVP and preterm births, especially, very preterm births and extremely preterm births.

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Background Some studies have indicated that female birth and multiple births were risk factors for nausea and vomiting during pregnancy (NVP). The results, however, were conflicting. Our study was conducted to evaluate the association of maternal NVP with fetal sex in singleton and twin pregnancies. Methods We used the data set from a birth cohort study, the Japan Environment and Children’s Study (JECS). In the self-administered questionnaire, participants were asked whether they experienced NVP prior to 12 gestational weeks. Main outcome measures were the presence of NVP and severity of NVP. We estimated the association of fetal sex and birth plurality with NVP using logistic regression analysis, followed by interaction analysis. Results Of 91,666 women, 75,828 (82.7%) experienced at least some symptoms of NVP and 10,159 (11.1%) experienced severe NVP. Women with female pregnancies and twin pregnancies had higher odds for the presence of NVP and severe NVP compared to women with male pregnancies and singleton pregnancies, respectively. Moreover, of mothers with twin pregnancies, higher odds for the presence of NVP and severe NVP were reported when one or both infants were female, compared to those in which both infants were male. There was no significant interaction between fetal sex and birth plurality. Conclusions Female sex birth and multiple births are risk factors for the presence of NVP, and especially for severe NVP without interaction. These findings suggest that a factor abundant in the female fetus associates with the severity of NVP.

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Objective: Postpartum depression (PPD) is a global emotional distress that affects women and their offspring regardless of their culture. The association between nausea and vomiting of pregnancy (NVP) and PPD has been widely described only for the severe form of NVP. We aimed to assess the relationship between PPD and NVP with regards to its severity. Methods: Data from the Japan Environment and Children's Study (JECS), a birth cohort study, were analyzed. PPD was assessed using the Edinburgh Postnatal Depression Scale (EPDS). Multiple logistic regression models were performed to assess the association between NVP and PPD. Results: Out of the 80,396 women included in the study 14% had PPD. Among them 4,640 (42.1%) had mild NVP; 3,295 (29.9%) had moderate NVP whereas 1,481 (13.4%) had severe NVP. All forms of NVP were associated with PPD and the association gradually increased with the severity of NVP symptoms with odd ratio (