Obstetric outcomes of twin pregnancies presenting with a complete hydatidiform mole and coexistent normal fetus: a systematic review and meta-analysis.

<bold>Background: </bold>Epidemiological data on obstetric and oncologic complications in twin pregnancies combining a complete hydatidiform mole (CHM) coexisting with a normal fetus and placenta are limited.<bold>Objectives: </bold>To evaluate perinatal and obstetric outcomes for mother and fetus and risk of gestational trophoblastic neoplasia (GTN) in twin pregnancies including a CHM.<bold>Search Strategy: </bold>PubMed, MEDLINE and EMBASE and the grey literature were searched for articles published between May 1980 and May 2019 using a protocol designed a priori and registered on PROSPERO (CRD42018112524).<bold>Selection Criteria: </bold>Observational cohort studies of four or more cases confirmed by histopathology and providing data on pregnancy outcomes and GTN.<bold>Data Collection and Analysis: </bold>Two reviewers independently reviewed abstracts and full-text articles. The quality of the studies was assessed with the Newcastle-Ottawa scale and a meta-analysis was performed.<bold>Main Results: </bold>Of the 344 abstracts identified, 14 studies (244 cases) met the eligibility criteria. The incidence of maternal complication in ongoing pregnancies was 80.8% and included vaginal bleeding, hyperthyroidism and pre-eclampsia. There were overall 91 (50%) live births in ongoing pregnancies and 83 (34%) of the total cases were subsequently diagnosed with GTN. Substantial and significant (P < 0.001) heterogeneity was found for the incidence of preeclampsia indicating variability in reporting the incidence of some obstetric complications between studies.<bold>Conclusions: </bold>Patients diagnosed with a twin pregnancy combining a CHM and an apparently normal fetus have a high risk of perinatal complications, low live-birth rates and around a third of them will develop a GTN and should be managed by specialised multidisciplinary teams.<bold>Tweetable Abstract: </bold>Our study indicates a high rate of obstetric and oncologic complications in patients presenting with a complete hydatidiform mole and coexistent normal fetus. [ABSTRACT FROM AUTHOR]