Maternal social deprivation and preterm birth: The PreCARE cohort study

Background: Maternal exposure to unfavourable social conditions is associated with a higher rate of perinatal complications, such as placental vascular pathologies. A higher risk of preterm birth (PTB) has also been reported, and variations across studies and settings suggest that different patterns may be involved in this association. Objective: To assess the association between maternal social deprivation and PTB (overall and by phenotype). Methods: We analysed 9365 patients included in the PreCARE cohort study. Four dimensions (social isolation, insecure housing, no income from work and absence of standard health insurance) defined maternal social deprivation (exposure). They were considered separately and combined into a social deprivation index (SDI). The associations between social deprivation and PTB <37 weeks (primary outcome) were analysed with univariable and multivariable log-binomial models (adjusted for maternal age, parity, education level and birthplace). Then we used multinomial analysis to examine the association with preterm birth phenotypes (secondary outcome): spontaneous labour, preterm prelabour rupture of membranes (PPROM) and placental vascular pathologies. Results: In all, 66.3%, 17.8%, 8.9% and 7.0% of patients had an SDI of 0, 1, 2 and 3, respectively. Social isolation affected 4.5% of the patients, insecure housing 15.5%, no income from work 15.6% and no standard health insurance 22.4%. Preterm birth complicated 7.0% of pregnancies (39.8% spontaneous labour, 28.3% PPROM, 21.8% placental vascular pathologies and 10.1% other phenotypes). Neither the univariable nor multivariable analyses found any association between social deprivation and the risk of preterm birth overall (SDI 1 versus 0: aRR 1.02, 95% confidence interval [CI] 0.83, 1.26; 2 versus 0: aRR 1.05, 95% CI 0.80, 1.38; 3 versus 0: aRR 0.92, 95% CI 0.66, 1.29) or its different phenotypes. Conclusions: In the French PreCARE cohort, we observed no association between markers of social deprivation and the risk of preterm birth, regardless of phenotype.