Delivery of Euthyroid Baby following Hyperthyroidism in Twin Gestation with Coexisting Complete Hydatidiform Mole

CONTEXT: Gestational trophoblastic disease (GTD) is a rare complication of pregnancy, ranging from molar pregnancy to choriocarcinoma. Twin pregnancies with GTD and coexisting normal fetus are extremely rare with an estimated incidence of 1 case per 22,000–100,000 pregnancies. Molecular mimicry between human chorionic gonadotrophin (hCG) and thyroid-stimulating hormone (TSH) leads to gestational trophoblastic hyperthyroidism (GTH) which is further associated with increased maternal and fetal complications. This is the first reported case in literature describing the delivery of a baby with biochemical euthyroid status following a twin pregnancy with hydatidiform mole (HM) associated with gestational trophoblastic hyperthyroidism (GTH). CASE DESCRIPTION: A 24-year-old G4 P3 Caucasian female with twin gestation was admitted to hospital for gestation trophoblastic hyperthyroidism. She was later diagnosed to have twin pregnancy with complete mole and coexisting normal fetus complicated by gestational trophoblastic hyperthyroidism (GTH). Despite the risk associated with the continuation of molar pregnancy, per patient request, pregnancy was continued till viability of the fetus. The patient underwent cesarean section due to worsening preeclampsia and delivered a euthyroid baby at the 24th week of gestation. CONCLUSIONS: Twin pregnancy with gestational trophoblastic disease and coexisting normal fetus is associated with high risk of hyperthyroidism, and careful monitoring of the thyroid function test along with dose titration of thionamides is of utmost importance throughout the gestation. If normal thyroid hormone levels are maintained during the pregnancy, euthyroidism could be successfully achieved in the baby.