The chance of recurrence of hyperemesis gravidarum: A systematic review

Around 1 % of pregnancies develop Hyperemesis Gravidarum (HG), causing high physical and psychological morbidity. Reports on HG recurrence rate in subsequent pregnancies vary widely. An accurate rate of recurrence is needed for informed reproductive decision making. Our objective is to systematically review and aggregate reported rates for HG subsequent to index pregnancies affected by HG. We searched databases from inception as per the protocol registered on PROSPERO. No language restrictions were applied. Inclusion was not restricted based on how HG was defined; reports of severe NVP were included where authors defined the condition as HG. We included descriptive epidemiological, case control and cohort study designs. Eligibility screening was performed in duplo. We extracted data on populations, study methods and outcomes of significance. A panel of patients reviewed the results and provided discussion and feedback. Quality was assessed with the JBI (2017) critical appraisal tool independently by two reviewers. We performed the searches on 1st November 2019. Our search yielded 4454 unique studies, of which five (n = 40,350 HG cases) matched eligibility criteria; One longitudinal and four population-based cohort studies from five countries. Follow-up ranged from 2 to 31 years. Definition of HG and data collection methods in all the studies created heterogeneity. Quality was low; studies lacked valid and reliable exposure, and/or follow-up was insufficient. Meta-analysis was not possible due to clinical and statistical heterogeneity. This systematic review found five heterogeneous studies reporting recurrence rates from 15 to 81%. Defining HG as hospital cases may have introduced detection bias and contribute to clinical heterogeneity. A prospective longitudinal cohort study using an internationally agreed definition of HG and outcomes meaningful to patients is required to establish the true recurrence rate of HG.