A national study on maternal vomiting during pregnancy in Iran: prevalence, determinants, adverse birth outcomes, and the trend.

Background: Nausea and vomiting during pregnancy (NVP) is one of the most common complication of pregnancy. The present study was aimed to determine the association between vomiting during pregnancy and adverse birth outcomes.

Methods: A cross-sectional study was conducted on 3649 pregnant women across 11 provinces of Iran. Cluster sampling method was used to select samples and data collection was done using family record and face-to-face interviews. Data were analyzed by logistic regression, using STATA14.2 software.

Results: The prevalence of vomiting during pregnancy was 9.7% (95% CI: 8.8, 10.7), with an increasing trend by birth cohort. After adjusting for other confounders, the prevalence of vomiting revealed a decreasing trend by body mass index (OR = 0.63, 95%CI: 0.53, 0.78, P-trend < 0.001). In addition, long inter-pregnancy interval (IPI) significantly increased the odds of NVP (OR_{IPI of 1-3 year}=2.42, OR_{IPI of >3 year}=1.63). Multivariate analyses showed that the odds of stillbirth (AOR = 1.61, 95% CI: 1.17, 2.19) and the odds of infant mortality (AOR = 1.78, 95% CI: 1.29, 2.45) were significantly increased in women with daily vomiting during pregnancy. The odds of vomiting during pregnancy was significantly shown to reduce the odds of abortion by 45%.

Conclusion: The prevalence of NVP was shown to have an increasing trend in Iran. This complication is associated with many adverse health outcomes during pregnancy and negatively affect maternal and fetal health. Given the importance of pregnancy period, nutrition education and increase the awareness of pregnant women towards NVP, especially pre-pregnancy training is suggested.