Background Extremely preterm infants (EPI) risk impaired neurodevelopmental outcomes. About one third of EPI develop intraventricular haemorrhage (IVH), a complication that increases the risk of impaired neurodevelopmental outcome in preterm infants. The outcome for EPI with IVH grade 1–2 remains unclear.

Aims To determine the impact of IVH grade 1–2 in EPI on neurodevelopmental outcome at 2.5 years of corrected age (CA).

Methods In this prospective population based cohort study the participants consisted of 707 EPI born alive before 27 weeks of gestation; EPI without IVH, EPI with IVH grade 1–2 and 3–4 respectively, and 701 full term controls. They were assessed and compared according to the Bayley scales of infant and toddler development, 3d edition (BSITD) and at 2.5 years of CA.

Results 70% of the live-born infants survived until the follow-up at 2.5 years of CA. The estimated marginal means (EMM) BSITD scores for EPIs with IVH grade 1–2 were not significantly lower than for EPIs without IVH in cognitive (p = 0.32, EMM = 86.8, CI = 82.5–91.1), language (p = 0.25, EMM = 88.8, CI = 82.0–95.6) or motor (p = 0.2, EMM = 78.8, SE = 3.8, CI = 71.308–86.376) functions.

Conclusions Although extremely preterm birth alone is a risk factor for impaired neurodevelopmental outcome, IVH grade 1–2 does not significantly increase that risk.