To investigate the neurodevelopmental outcome at age 2 and 5 years in survivors of twin–twin transfusion syndrome (TTTS) treated with fetoscopic laser surgery and born premature and/or small for gestational age.

At 2 and 5 years of age, standardized neurologic, motor, and cognitive assessments were performed by a neonatologist, a pediatric physical therapist, and a psychologist. Behavior was assessed using a validated questionnaire completed by parents.

Neurodevelopmental assessment at both time points was available for 73 survivors of TTTS. Mild to moderate neurodevelopmental impairment (NDI) was detected in 34% of survivors (25 of 73) at 5 years, compared with 25% (18 of 73) at 2 years (P = .178). Severe NDI was observed in 12% (9 of 73) at 5 years and in 3% (2 of 73) at 2 years (P = .035). Mean cognitive score was lower at the 5-year follow-up (90.7 ± 12.3 vs 95.6 ± 13.1 at 2 years; P = .001), and more children were diagnosed with mild cognitive impairment at 5 years (29% vs 11% at 2 years; P = .007). When comparing individual outcomes at both time points, 35% (25 of 71) moved from a normal outcome or mild to moderate impairment at 2 years toward more severe impairment at 5 years.

A high rate of mild to moderate cognitive impairment and severe NDI at age 5 years was not identified at age 2 years. Our data highlight the importance of longitudinal follow-up of survivors of TTTS beyond age 2 years and emphasize the precautions that should be taken when diagnosing an absence of impairment before school age.