Objective: To review the prevalence and risk factors for severe neurodevelopmental impairment (NDI) in infants born at 22-29 weeks of gestation without severe intraventricular hemorrhage (IVH) or periventricular leukomalacia (PVL).

Methods: This single-centered retrospective cohort study enrolled infants born at 22-29 weeks of gestation treated at Saitama Medical Center, Saitama Medical University, from 2005 to 2020. Patients with severe IVH or PVL were excluded. The primary outcome was severe NDI at 3 years of age, defined by the presence of neurodevelopmental delay (developmental quotient <70), severe cerebral palsy, or severe sensory deficit. The incidence of severe NDI was assessed, and its associated risk factors were analyzed using multivariable logistic regression.

Results: A total of 666 patients were analyzed, including 134 (20 %) who developed severe NDI. The prevalence of severe NDI was high among infants born at 22 weeks (19/26, 73 %) and 23 weeks (17/50, 34 %) of gestation. A multivariable logistic regression analysis with previously known predictors showed that lower birth weight, male sex, no antenatal corticosteroid therapy, and abdominal surgery were independently associated with severe NDI at 3 years of age.

Conclusions: As shown in previous studies, a high prevalence of severe NDI was observed in our cohort. Infants born at 22 and 23 weeks of gestation have a high risk of severe NDI even though they are without severe IVH or PVL. Antenatal corticosteroid therapy were beneficial for preventing severe NDI. Infants with a history of abdominal surgery require close monitoring for their neurodevelopmental outcomes.