A National Study of Maternal Vomiting During Pregnancy in Iran: Prevalence, Determinants, Adverse Birth Outcomes and the Trend | BMC Pregnancy and Birth

The results of univariate analysis showed that maternal age, stillbirth, maternal overweight and obesity, abortion, parity ≥ 4, first pregnancy, and IPI of two and three years were significantly associated with vomiting during pregnancy. However, multivariate analysis showed a significant association between vomiting during pregnancy and two-year maternal BMI and IPI.

In the present work, the prevalence of NVP and related factors was pointed out. The results of our study show that 9.7% of women experienced vomiting during pregnancy. The quality of life of pregnant women is severely affected by NVP, a common pregnancy complication. This condition can lead to disability in some women and, as a result, spontaneous abortion. Although numerous studies have focused on NVP, the cause of NVP is still unclear [8, 12, 14]. The results of our study were reported by Bai et al. supports. [15] However, the prevalence of NVP was lower than the rates reported in Spanish, Chinese, and other Iranian studies, which reported the NVP rate as 29.3, 30, and 71.5%, respectively [1, 4, 16]. These contradictory results may be due to different research methods and different effects of this condition, so some studies have examined nausea and vomiting during pregnancy together.

The results of the present study suggest that vomiting during pregnancy was significantly associated with maternal BMI, that is, increased BMI reduced the prevalence of vomiting during pregnancy. Jenabi and colleagues found that pregnant women who reported vomiting episodes in the first trimester of pregnancy had lower BMI levels [17]. Another study showed that both obesity and being underweight were associated with vomiting during pregnancy [18]. According to the literature, it is believed that underweight women have low estrogen levels before pregnancy and that increased estrogen levels during pregnancy increase the risk of NVP [19].

The results of this study also show that two years of IPI increases the likelihood of NVP. Elevated IPI is thought to increase the risk of hyperemesis gravidarum (HG). Women with a history of NVP in the first pregnancy may be prone to longer IPIs, while fertility rates are lower in women with HG [20]. Most relevant studies have demonstrated the association between IPI and pregnancy outcomes, including low birth weight, preterm birth, and stillbirth [21, 22]. Women with a history of severe vomiting during pregnancy may be more likely to have prolonged IPI due to NVP complications. As a result, her hormone levels are at the same level as in the first or previous pregnancy due to long IPIs. However, further research is needed to examine the association between IPI and NVP in more detail.

This study found that maternal age at pregnancy significantly increased the likelihood of NVP, which was consistent with previous studies [23,24,25]. The results of Bazarganipour et al. did not agree with the results of our study [4]. We also found that levels of human chorionic gonadotropin (HCG) increase during pregnancy, which are higher at younger ages and may lead to a higher risk of vomiting during pregnancy [26].

Crozier and colleagues suggested that women with lower levels of education experienced more severe nausea during pregnancy [27]. In our study, there was a significant association between maternal education and vomiting during pregnancy, while other studies found no association between NVP and maternal education [1, 28]. Pregnant women with less education are more likely to have low health literacy. This can lead them to not properly follow the advice of various midwifery specialists, which can ultimately lead to a poor quality of life at this stage.

The results of this study showed a significant association between a history of abortion and vomiting in pregnancy. Studies in different countries have shown that NVP cannot increase the likelihood of abortion due to unfavorable conditions for the mother [29, 30]. Although vomiting during pregnancy is not a threatening risk factor for abortion, the health-threatening complications associated with this condition, such as maternal and fetal weight loss, should not be ignored [25]. Because the study was a cross-sectional design, women with a history of abortion may have effective strategies to reduce the severity of nausea to avoid unintentional NVP.

The results of our study also showed a significant increasing trend in NVP in recent years. Louik and colleagues reported no increased risk of NVP during their study period [31]. No previous study has examined the prevalence of NVP in different time periods. Therefore, further research to assess the trend of NVP is recommended.

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This was a cross-sectional study and interpretation of casual relationships was limited. Additionally, due to the use of self-reported data, recall bias was likely to occur during the data collection process. In addition, this study did not collect data on the patient’s diet and food allergy, which may have a significant impact on the severity of NVP. Nevertheless, it was a national Iranian study with an acceptable sample size that could be generalized to the general population.