BACKGROUND: Singleton normal fetus with partial hydatidiform mole (PHM) pregnancy is a rare phenomenon. No previous reports have investigated the risk factors of gestational trophoblastic neoplasia (GTN) progression following this condition.
METHODS: We retrospectively enrolled cases of singleton normal fetuses with PHM pregnancies at West China Second University Hospital, Sichuan University, from 2005 to 2017. Other cases were identified from PubMed databases during 1975 to 2021 for the cohort study. Cox proportional hazards models were applied to evaluate risk factors for GTN progression based on the patient\'s clinical characteristics.
RESULTS: Overall, 36 cases of singleton normal fetuses with PHM pregnancies were enrolled. After a median follow-up of 4.0 (0.8-12.0) months, nine (25.0%) patients progressed to GTN. Gestational age at pregnancy termination (hazard ratio [HR] 0.88; 95% confidence interval [CI] 0.78-0.99, p = 0.032), hyperthyroidism (HR 5.75; 95% CI, 1.16-28.50, p = 0.032), and reasons for pregnancy termination (medical indications vs. patients\' choice; HR 0.25; 95% CI, 0.06-0.99, p = 0.049) were significantly correlated with GTN progression. Area under the receiver operating characteristic curve (AUC) of gestational age at pregnancy termination to predict non-progression to GTN was 0.784 (95% CI, 0.615-0.903, p < 0.001). A clinically significant cutoff value, that is, gestational age of 24 weeks, was determined by comprehensively considering the cutoff values of AUC and clinical significance of gestational age.
CONCLUSIONS: Compared to gestational age of pregnancy termination <24 weeks, ≥24 weeks was a protective factor for GTN. Therefore, there is enough evidence to continue pregnancy, except for uncontrolled severe complications, without increasing the risk of GTN progression.

Complete hydatidiform (also referred to as hydatiform) mole with coexisting live fetus is an exceedingly rare event. The fetus usually has a normal karyotype, and approximately 25-40% chance of survival, if pregnancy is allowed to continue until reasonable fetal lung maturity is achieved. However, risk of maternal complications including preeclampsia and subsequent trophoblastic disease are significant. We report a case of a 19-year-old primigravida, at 25 weeks gestation with a complete hydatidiform mole and a coexisting live fetus. She developed severe preeclampsia with uncontrolled hypertension, and pregnancy was terminated by caesarean section, after a short course of dexamethasone to accelerate fetal lung maturity. A morphologically normal live female fetus and placenta were delivered without complications, along with a separate mass of complete mole. The postpartum course was complicated by uterine choriocarcinoma with metastases to lung and left kidney, which responded to chemotherapy. Our case is a rare example of a twin gestation composed of a complete hydatidiform mole with a coexisting live fetus, and illustrates the associated spectrum of maternal complications that mandate close pre- and post-natal surveillance.