Complete hydatidiform mole with coexistent twins following in vitro fertilisation

A 40-year-old primi who conceived through IVF presented with pre-eclampsia at 19 weeks gestation. She also has poorly controlled gestational diabetes mellitus, on treatment with oral hypoglycemic agents and long-standing hypothyroidism requiring levothyroxine therapy. Cervical incompetence was also detected, requiring cerclage at 14 weeks.

Anomaly scan showed two live fetuses (dichorionic diamniotic) and a multi-cystic mass without colour Doppler signal, adjacent to the placenta. There was inter-twin discordance in estimated fetal weight of 31.1% and echogenic bowel in smaller twin. She underwent fetal MRI, which revealed a heterogeneous intrauterine mass, based along the posterior wall, with numerous T2 hyperintense cystic spaces. No obvious fetal part was noted within the mass. Multiple fibroids were also noted. Beta-hCG level at the time of scan was 47,683 IU/L which when repeated after 12 days showed tremendous rise to 318,548 IU/L. Follow-up ultrasound scans after 3 weeks and 6 weeks showed inter-twin discordance of 36.1% and 41.1%, respectively. Umbilical artery doppler in the last scan revealed reversal of diastolic flow in the smaller fetus and absent end diastolic flow in the other.

Background

Hydatidiform mole with coexistent fetus is a very rare entity with an incidence of 0.001 to 0.01% [1]. It usually occurs in one of two ways: complete hydatidiform mole with coexistent twin fetus (CHMTF) or partial mole with abnormal triploid fetus. The latter is a fatal condition with spontaneous first-trimester abortion as the usual outcome, owing to severe fetal anomalies. In CHMTF, the fetus is usually spared of anomalies, but the prognosis is guarded due to higher incidence of possible complications such as spontaneous miscarriage, intrauterine fetal demise, severe pre-eclampsia, severe vaginal bleeding, preterm delivery and gestational trophoblastic neoplasia (GTN) [2]. CHMTF may also occur following assisted reproductive techniques such as IVF, as in our case. Oocyte manipulation during IVF may disrupt the meiotic spindle leading to loss of maternal chromosomes, which can contribute to development of a complete mole [3].

Clinical perspective

CHMTF may present with complications such as pre-eclampsia, vaginal bleeding, hyperthyroidism, hyperemesis, abortion, intrauterine death and GTN [4]. An early obstetric USG may yield the first clue to diagnosis in an asymptomatic patient [5]. Early prenatal diagnosis of CHMTF is imperative, so as to decide upon termination of pregnancy and to actively surveil for the development of GTN. CHMTF needs to be distinguished from placental mesenchymal dysplasia (PMD). Both conditions have similar clinical and ultrasound findings. Beta-hCG elevation, which is characteristic of gestational trophoblastic diseases, has been observed in some cases of PMD [2].

Imaging perspective

Complete mole appears as a multicystic mass, often with vascularity on colour Doppler. The grey-scale appearance is described as resembling ‘snowstorm’ or ‘bunch of grapes’. In MRI, the lesion appears as heterogeneous multicystic mass without any fetal part. Intralesional haemorrhage and bilateral theca lutein cysts may be seen. In contrast, PMD appears as multicystic changes occurring within the placenta. In our case, diagnosis was confirmed postpartum by histopathological examination, which showed trophoblastic proliferation in the mass [2].

Outcome

CHMTF patients have greater risk of perinatal complications, as already described [4]. A significant proportion develop GTN, thus requiring active surveillance [5]. In our case, owing to the abnormal umbilical artery doppler, pregnancy was terminated at 27 weeks through emergency caesarean section. Unfortunately, both the babies expired during neonatal period.

Take home message

A multicystic intrauterine lesion coexisting with live fetus should raise concern for CHMTF. It has to be distinguished from PMD based on the location of the lesion: extraplacental – CHMTF; intraplacental – PMD.

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