Evaluation of area based socioeconomic inequalities and neonatal mortality rates in France: national population based...

To investigate the magnitude and evolution of inequalities in neonatal mortality rates by using area based socioeconomic indices in France.

National population based study.

For 2015-20, data from the French National Health Data System (Système National des Données de Santé, SNDS). For 2001-08, neonatal death certificates and aggregate vital statistics data by municipality of residence.

Live births with a gestational age ≥22 completed weeks to a mother residing in metropolitan France, 2015-20 (4 293 403 live births and 10 869 neonatal deaths), compared with a 2001-08 study (6 202 918 live births and 14 851 neonatal deaths).

Differences in neonatal mortality rate (death before day 28 of life) according to the socioeconomic characteristics of the mother's municipality of residence. Comparison with data from a 2001-08 study to assess changes in socioeconomic inequalities and their contribution to the increase in neonatal mortality rate.

The neonatal mortality rate was 2.53 per 1000 live births in 2015-20. Five indicators, previously associated with perinatal mortality, were combined into a perinatal French deprivation index (P-FDep) for the main analysis. P-FDep was categorised into five equal groups (deprivation groups 1-5) for comparison with other research and into 10 equal groups (deprivation groups 1-10) for more granular analyses, with group 1 being the least and group 5 (or group 10) the most deprived group. The rate in the most deprived compared with the least deprived group for P-FDep was 1.71 (95% confidence interval 1.60 to 1.83) times higher, based on the analysis of deprivation groups 1-5. A mortality gradient existed across the groups, translating into 2496 excess deaths (23.3%) when the rate in the least deprived group was applied to all areas. The gradient was more marked when deprivation groups 1-10 were used (relative risk 1.88, 95% CI 1.71 to 2.07 for the highest to the lowest deprived group). Compared with 2001-08 (neonatal mortality rate 2.39 per 1000), the rate remained constant in the least deprived areas, but worsened in the most deprived areas (+10.1% and +11.7% for groups 4 and 5, respectively), increasing the relative risks between the highest and lowest groups, which were 1.54 (95% CI 1.46 to 1.62) for deprivation groups 1-5 and 1.67 (1.55 to 1.79) for deprivation groups 1-10, in 2001-08.

In this study, the socioeconomic level of the mother's place of residence was strongly associated with the neonatal mortality rate. The data showed that inequalities have widened, contributing to the increase in the neonatal mortality rate.