Complete Molar Pregnancies with a Coexisting Fetus: Pregnancy Outcomes and Review of Literature

To review obstetric outcomes of complete hydatidiform molar pregnancies with a coexisting fetus (CHMCF), a rare clinical entity, we performed a retrospective case series of pathology-confirmed HMCF. The cases were collected via a private Maternal-Fetal Medicine physician group on social media. Each contributing institution from across the United States obtained informed consent and institutional data transfer agreements as required, then transmitted the data using a HIPAA-compliant modality. Data collected included maternal, fetal/genetic, placental and delivery characteristics. Nine institutions contributed 14 cases. We found that the median gestational age at diagnosis was 12 weeks 2 days (9w0d - 19w4d), and over half were diagnosed in the first trimester. Sixty-four percent of CHMCF cases were a product of assisted reproductive technology. Placental mass size universally enlarged over the surveillance period. When invasive testing was performed, insufficient sample or no growth was noted in 40% of the sampled cases. Antenatal complications occurred in all delivered patients. Four patients developed gestational trophoblastic neoplasia. This is the largest reported series of obstetric outcomes for CHMCF, and highlights the need to counsel patients about the severe maternal and fetal complications in continuing pregnancies, including progression to gestational trophoblastic neoplastic disease.