Pregnancy outcomes by hyperemesis gravidarum severity and time of diagnosis: A retrospective cohort study

Objective: With inconsistencies regarding the possible effect of hyperemesis gravidarum on the course of pregnancy, this research aimed to study the association between hyperemesis gravidarum and pregnancy outcomes, while also addressing the trimester of diagnosis and severity. Methods: A retrospective cohort study was performed, including all singleton deliveries of mothers from the largest health maintenance organization in the country, in a single tertiary hospital between 1991 and 2021. The incidence of adverse pregnancy outcomes was compared between pregnancies with and without hyperemesis gravidarum diagnosis. Multivariable generalized estimation equation binary models were used to study the association between maternal hyperemesis gravidarum, trimester of diagnosis and hyperemesis gravidarum severity and the studied outcomes. Results: The study population included 232 476 pregnancies, of which 3227 (1.4%) were complicated with hyperemesis gravidarum. Women with hyperemesis gravidarum were more likely to deliver preterm (adj. OR = 1.33, 95% CI: 1.18–1.50), a newborn with low birthweight (adj. OR = 1.52, 95% CI: 1.16–1.98, only if diagnosed in the second trimester), and to have a cesarean delivery (adj. OR = 1.20, 95% CI: 1.09–1.32). They were less likely to deliver small gestational age newborn (adj. OR = 0.82, 95% CI: 0.69–0.99) and their offspring to experience perinatal mortality (adj. OR = 0.54, 95% CI: 0.31–0.93, among mild cases only). A dose–response association was observed between preterm birth and hyperemesis gravidarum (adj. OR = 1.26; 95% CI: 1.11–1.44, for mild cases and adj. OR = 2.04; 95% CI: 1.31–3.19, for severe cases). Conclusions: Hyperemesis gravidarum is associated with an increased risk for adverse pregnancy outcomes including mainly preterm delivery in a dose–response manner and when diagnosed during the second trimester.