Objective To compare neurodevelopmental outcomes of extremely preterm infants conceived after assisted conception (AC) compared with infants conceived spontaneously (non-AC).

Design Population-based retrospective cohort study.

Setting Geographically defined area in New South Wales and the Australian Capital Territory, Australia served by a network of 10 neonatal intensive care units.

Patients Infants <29 weeks’ gestation born between 1998 and 2004.

Intervention At 2–3 years corrected age, 1473 children were assessed with either the Griffiths Mental Developmental Scales or the Bayley Scales of Infant Development.

Main outcome measure Moderate/severe functional disability defined as developmental delay (Griffiths General Quotient or Bayley Mental Developmental Index >2 SD below the mean), cerebral palsy (unable to walk without aids), deafness (bilateral hearing aids or cochlear implant) or blindness (visual acuity <6/60 in the better eye).

Results Mortality and age at follow-up were comparable between the AC and non-AC groups. Developmental outcome was evaluated in 217 (86.5%) AC and 1256 (71.7%) non-AC infants. Using multivariate adjusted analysis, infants born after in-vitro fertilisation at 22–26 weeks’ gestation (adjusted OR 1.79, 95% CI 1.05 to 3.05, p=0.03) but not at 27–28 weeks’ gestation (adjusted OR 0.81, 95% CI 0.37 to 1.77; p=0.59) had higher rate of functional disability than those born after spontaneous conception.

Conclusions AC is associated with adverse neurodevelopmental outcome among high risk infants born at 22–26 weeks’ gestation. This finding warrants additional exploration.