Objective Evaluate the incidence of and risk factors for behavioural problems in twin–twin transfusion syndrome (TTTS) survivors treated with fetoscopic laser coagulation.

Design Observational cohort study.

Setting National referral center for fetal therapy, Leiden University Medical Center, The Netherlands.

Patients Behavioural outcome was assessed in 417 TTTS survivors, at the age of 2 years.

Interventions Parents completed the Child Behavior Checklist for their twins. Antenatal, neonatal and follow-up data including Bayley III and a neurological exam were recorded from the medical database.

Main outcome measures The incidence of and risk factors for behavioural problems.

Results 332 twin pregnancies (664 fetuses) were treated with fetoscopic laser for TTTS between 2008 and 2015. For 517 children eligible for follow-up, 417 (81%) Child Behavior Checklist questionnaires were completed. The study group was born at a mean gestational age of 32.8 weeks±3.2. Total behavioural problems within the borderline to clinical range were reported in 8% (95% CI 5.9 to 11.2) of survivors, compared with 10% in the general Dutch population (p=0.12). No difference between donors and recipients was detected (p=0.84). Internalising and externalising problems were reported in 9.4% (95% CI 6.9 to 12.6) and 11.5% (95% CI 8.8 to 15.0), respectively. Severe neurodevelopmental impairment was more frequent in the children with behavioural problems. High maternal educational level was associated with lower behavioural problem scores.

Conclusion Parents of twins treated with fetoscopic laser therapy for TTTS do not report more behavioural problems compared with general population norms. More behavioural problems are reported in children with severe neurodevelopmental impairment.