Trends in the incidence of low-grade intraventricular haemorrhage among preterm babies: a national cohort study

OBJECTIVE: To assess regional and temporal variation and influencing factors of low-grade intraventricular haemorrhage (IVH) incidence among preterm infants admitted to neonatal units in England. DESIGN: Population cohort study SETTING: England, UK. PATIENTS: All infants born <34 weeks' gestation between 2008 and 2019 admitted to a National Health Service neonatal unit in England (n=165 269). EVENT: Low-grade IVH (grade 1-2). MAIN OUTCOME MEASURES: Crude incidence rates and adjusted incidence rate ratios (IRRs) from Poisson models comparing calendar years, geographically defined operational delivery networks, sex and gestation. RESULTS: Low-grade IVH occurred in 8.7% (14 415/165 269) of preterm admissions. Crude incidence increased from 6.8% in 2008-2009 to 10.1% in 2018-2019. After adjustment for gestation, sex and neonatal network, incidence in 2018-2019 was higher than in 2008-2009 (adjusted IRR 1.64, 95% CI 1.51 to 1.79). Both grade 1 and grade 2 IVH rose over time. Geographical heterogeneity was pronounced: low-grade IVH incidence ranged from 2.6% to 15.9% across networks, a more than sixfold difference that persisted after case-mix adjustment. Temporal patterns also diverged by network, some showed high and rising incidence over time, while others remained lower or stable. CONCLUSION: Low-grade IVH is common among preterm admissions and recorded incidence increased between 2008 and 2019, with consistent gestational and sex patterns and substantial geographical variation. The contribution of interobserver diagnostic variability to this variation is unknown; nonetheless, the magnitude and consistency of the trends suggest a rising, potentially uneven burden of low-grade IVH in England, warranting further investigation to inform quality improvement interventions.