Objective Remind pediatricians of the differential diagnosis of discordant twins.
Case A 21-year-old primigravid woman with EGA of 32 weeks by LMP with minimal prenatal care presented with preterm labor fully dilated. Ultrasonography revealed a twin gestation with size discordance and absent fetal heart tones in twin A. Prenatal laboratory tests were unavailable. The twins were delivered by emergent cesarean section, with twin A having Apgar scores of 0, 2, and 6 at 1, 5, and 10 minutes and twin B having Apgar scores of 4, 7, and 9. Physical examination of twin A revealed a 530 g girl with lens vascularization and neurologic evaluation consistent with a less than 28-week gestation and hematocrit of 44.7. Twin B was a 1,570 g girl with lens vascularization, neurologic evaluation, and other parameters consistent with a 32-week gestation and a hematocrit of 38.3. No congenital anomalies were found. The placenta was noted to be dichorionic, diamnionic, late second-trimester twin placenta with a two-vessel cord with a single umbilical artery for twin A and an eccentrically inserted three-vessel cord for twin B. No evidence of chorioamnionitis, funisittis, or villitis was found. Twin A had a complicated hospital course that included the need for HFOV, the development of NEC, hyperbilirubinemia, pulmonary HTN, AOP, and ROP but survived after almost 3 months in the NICU. Twin B required only initial ventilatory support and treatment with indomethacin for a PDA but otherwise had an uneventful 3-week hospital course. The mother denied any use of illicit drugs or alcohol but did admit to tobacco use. Maternal hypertension and DM were not evident at admission.
Discussion This case demonstrates extreme twin discordance due to idiopathic IUGR in twin A. Birth discordance occurs in approximately 10% of all twin gestations and is associated with an increased risk of fetal demise and increased neonatal morbidity and mortality. There is a higher rate of IUGR in multiples versus singletons, which is most likely a result of uteroplacental insufficiency related to increased fetal metabolic demands as well as abnormal placental implantation. Other causes of twin discordance, especially in monozygotic twins, include twin-twin transfusion and congenital anomalies. Twin-twin transfusion syndrome (TTTS) has a mortality rate as high as 80% in severe cases. Congenital anomalies associated with discordance include anencephaly, holoprosencephaly, VATER associations, placental vascular shunts, and conjoining. Physicians should be prepared to evaluate discordant twins and identify and treat the associated medical complications of IUGR, TTTS, and/or congenital anomalies.
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