Diagnosis and outcome of hydatidiform moles in missed-miscarriage: a cohort-study, systematic review and meta-analysis.

Objective: To evaluate the ultrasound diagnostic rates of complete hydatidiform moles (CHM) and partial hydatidiform moles (PHM) in women presenting with a missed miscarriage, the clinical complications at diagnosis and the risk of gestational trophoblastic neoplasia (GTN) after surgical evacuation and to compare our findings with those of the published literature by completing a systematic review and meta-analysis STUDY DESIGN: Retrospective review of the data of 295 women diagnosed with a histologically confirmed hydatidiform moles (HM) over a 15-year period, including 128 CHM and 167 PHM. All women were referred to a regional specialist centre for follow-up and further management. An electronic search of PubMed, Google Scholar and MEDLINE was performed for studies published between September 1973 and September 2017 reporting on the early ultrasound diagnosis of hydatidiform mole. Only cohort studies which provided ultrasound data confirmed by histopathology were included.

Results: In the cohort study, ultrasound imaging diagnosed a significantly (p < 0.001) higher number of CHM (95/128 (74.2%) than PHM (68/167 (40.7%). Ovarian theca lutea cysts were observed in three CHM and one PHM. There were no cases of pre-eclampsia or thyrotoxicosis at the time of diagnosis. Maternal serum β-human chorionic gonadotrophin levels were abnormally low (< 0.5 MoM) in 5/51 (10%) CHM and 23/43 (53%) PHM and abnormally high (> 2.0 MoM) in 20/51 (39%) CHM and 2/43 (5%) PHM. Seventeen (12.3%) CHM and two (1.4%) PHM developed a GTN requiring treatment. In the literature the proportion of histologically diagnosed HM, suspected on ultrasound in early pregnancy, ranged between 34.2 and 90.2% for HM, 57.8 and 95% for CHM and 17.6 and 51.6% for PHM. The meta-analysis indicated substantial heterogeneity in the overall ultrasound diagnosis of HM and in the differential diagnosis between CHM and PHM.

Conclusion(s): As around a third of CHM and two thirds of PHM are not diagnosed on ultrasound in cases of missed miscarriage, histopathological examination of all products of conception in case of early pregnancy failure is essential to detect molar changes. This is particularly important for the management of women with CHM who have a higher risk of developing a GTN.