Social patterns of miscarriage reporting and risk: insights from survey data in France.

Miscarriages, which are spontaneous pregnancy losses before 20-28 weeks of gestation, affect approximately 15% of recognized pregnancies. Existing population-based evidence of social inequalities in miscarriage risk is inconsistent, partly due to a lack of data. Surveys can be representative of a national population but are subject to underreporting of miscarriages. We examine whether miscarriages are underreported in a French nationally representative survey, FECOND (2010-11), and analyse socioeconomic risk factors for miscarriage. First, we apply a model that estimates miscarriage underreporting. Second, we use multilevel multinomial logistic regressions to examine socio-demographic and epidemiological factors associated with miscarriage. We estimate that 92% of miscarriages were reported, and underreporting was slightly more pronounced among lower-educated women. The estimated prevalence of miscarriages (14% of all pregnancies) is unaffected by underreporting rates and only with small educational differences. Thus, investigating social disparities in miscarriage risk can be done without correcting for reporting bias. Advanced reproductive ages are associated with higher miscarriage risk. Unobserved time-consistent individual characteristics explain the association between miscarriage risk and prior reproductive history. Conversely, education and self-assessed financial conditions are not associated with miscarriage risk. Younger cohorts exhibit a higher miscarriage risk, suggesting an age effect on recall, a cohort effect on pregnancy recognition, or reduced stigma resulting in more reliable reporting of miscarriage. In sum, the miscarriage reporting rate in FECOND survey is relatively high and with only slight social disparities. No large socioeconomic differences were found in miscarriage risk.