Persisting inequalities in birth outcomes related to neighbourhood deprivation.

Introduction: Health inequalities can be observed in early life as unfavourable birth outcomes. Evidence indicates that neighbourhood socioeconomic circumstances influence health. However, studies looking into temporal trends in inequalities in birth outcomes including neighbourhood socioeconomic conditions are scarce. The aim of this work was to study how inequalities in three different key birth outcomes have changed over time across different strata of neighbourhood deprivation.

Methods: Nationwide time trends ecological study with area-level deprivation in quintiles as exposure. The study population consisted of registered singleton births in the Netherlands 2003-2017 between 24 and 41 weeks of gestation. Outcomes used were perinatal mortality, premature birth and small for gestational age (SGA). Absolute rates for all birth outcomes were calculated per deprivation quintile. Time trends in birth outcomes were examined using logistic regression models. To investigate relative inequalities, rate ratios for all outcomes were calculated per deprivation quintile.

Results: The prevalence of all unfavourable birth outcomes decreased over time: from 7.2 to 4.1 per 1000 births for perinatal mortality, from 61.8 to 55.6 for premature birth, and from 121.9 to 109.2 for SGA. Inequalities in all birth outcomes have decreased in absolute terms, and the decline was largest in the most deprived quintile. Time trend analyses confirmed the overall decreasing time trends for all outcomes, which were significantly steeper for the most deprived quintile. In relative terms however, inequalities remained fairly constant.

Conclusion: In absolute terms, inequalities in birth outcomes by neighbourhood deprivation in the Netherlands decreased between 2003 and 2017. However, relative inequalities remained persistent.