Objective: To assess long term changes in cardiac morphology and function in survivors of severe twin to twin transfusion syndrome (TTTS) after intrauterine laser coagulation of placental anastomoses. Design: Prospective follow up of fetuses with severe TTTS treated by laser coagulation of intrauterine placental anastomoses. Fetal echocardiography and Doppler studies of feto-placental haemodynamic function were performed at the time of laser coagulation (median gestational age of 21.7 weeks). Postnatal cardiac follow up included a detailed echocardiographic study of systolic and diastolic cardiac function at a median age of 21.1 months. Setting: Paediatric cardiology unit. Patients: 89 survivors from 73 consecutive pregnancies with severe TTTS. Results: Before laser treatment, 28 of 51 (54.9%) recipient twins had typical signs of cardiac dysfunction due to volume overload and 9 of 38 (23.7%) donors had absent or reversed end diastolic flow in the umbilical artery. Echocardiography was normal in 87.6% of the survivors (34 of 38 donors, 44 of 51 recipients). The prevalence of congenital heart disease and particularly of pulmonary stenosis, which was recorded only in recipients, was increased in comparison with the general population (congenital heart disease, 10 of 89 (11.2%) v 0.3%; pulmonary stenosis, 4 of 51 (7.8%) v 0.03%). Findings before laser treatment were not correlated with the development of structural heart disease. Conclusions: Despite the high rate and severity of prenatal cardiac overload in recipients, the majority of cases of TTTS are normalised after laser treatment. However, given the increased prevalence of congenital heart disease and in particular pulmonary stenosis, intrauterine and postnatal follow up is warranted.

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