Measuring miscarriages: A comparison of self-reported and healthcare register data in Finland

BACKGROUND: Approximately one in four women experiences a miscarriage, which may affect fertility intentions and health. However, there is a lack of research on the topic, in part due to poor quality of miscarriage data. Both surveys and healthcare records likely miss some early pregnancy losses. We compare data from self-reports and healthcare records at the individual level to understand to what extent these data differ and for whom.METHODS: We used healthcare records on miscarriages in Finland linked to self-reported miscarriage data in antenatal appointments, as well as in a national epidemiological survey, FinHealth 2017. The antenatal data was available for all those with a live birth, whereas the survey also captured those without children, but had a smaller sample size. We compared the consistency of records overall and by socio-demographic characteristics using descriptive statistics and multinomial regressions.RESULTS: For over 80% of people, miscarriage data was consistent between self-reports and healthcare records. This was mainly driven by those who had never had a miscarriage, as the share of consistent records dropped to 40% when only those with at least one miscarriage in one data source were analysed. We observed some self-reporting fewer (1-4% among full sample, 7-13% among those with a miscarriage) and some more miscarriages than in healthcare records (8-12% among the full sample, 46-56% among those with a miscarriage). Inconsistency in either direction was often associated with older age, higher parity, and lower education.CONCLUSIONS: Healthcare records and self-reports overlap partly in the miscarriages they capture. More miscarriages were observed using self-reports, probably due to some miscarriages managed outside the healthcare system, and differences in miscarriage definition between lay people and healthcare professionals, with the latter having a more restrictive definition. Future miscarriage studies should carefully consider the strengths and limitations of each type of source against their research aims, when choosing a suitable data source.