Aims Findings concerning the impact of socio‐economic status on the risk of gestational diabetes mellitus (GDM) are inconclusive and little is known about the simultaneous impact of income and educational attainment on the risk of GDM. This study aims to assess the impact of maternal prepregnancy income in combination with traditional GDM risk factors on the incidence of GDM in primiparous women. Methods This is an observational cohort study including 5962 Finnish women aged ≥ 20 years from the city of Vantaa, Finland, who delivered for the first time between 2009 and 2015, excluding women with pre‐existing diabetes mellitus. The Finnish Medical Birth Register, Finnish Tax Administration, Statistics Finland, Social Insurance Institution of Finland and patient healthcare records provided data for the study. We divided the study population according to five maternal income levels and four educational attainment levels. Results Incidence of GDM decreased with increasing income level in primiparous women (P < 0.001 for linearity, adjusted for smoking, age, BMI and cohabiting status). In an adjusted two‐way model, the relationship was significant for both income (P = 0.007) and education (P = 0.039), but there was no interaction between income and education (P = 0.52). Conclusions There was an inverse relationship between both maternal prepregnancy taxable income and educational attainment, and the risk of GDM in primiparous Finnish women.

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Introduction: Preterm birth is a major cause of infant mortality. It is unknown whether body mass index (BMI) influences the risk of preterm birth in women, who prenatally use antidepressants.Materials and methods: The study cohort (N ¼ 6920) consists of all primiparous European born women without previously diagnosed diabetes from the city of Vantaa, Finland, who delivered a singleton child between 2009 and 2015. Data on births, pre-pregnancy BMI and purchases of antidepressants from 12 months before conception until delivery were obtained from Finnish National Registers. Results: Of the primiparous women, 9.9% used antidepressants. The overall prevalence of preterm birth was 5.2%. In women with a pre-pregnancy BMI <18.5 kg/m 2 , the Odds Ratio (OR) for preterm birth among antidepressant users compared with those who were non-users was 1.91 (95% confidence intervals [CI] 0.40 to 9.15, adjusted for age, smoking, education, use of fertility treatments and number of previous pregnancies) while in women with a pre-pregnancy BMI 30 kg/m 2 , the OR was 0.53 (95% CI 0.21-1.36), respectively. Discussion: Primiparous women using antidepressants, who were underweight before conception should be closely monitored and provided tailored care in a maternity clinic to minimize the risk of preterm birth. KEY MESSAGESIn primiparous women, one in ten used antidepressant medications before pregnancy and/or during pregnancy. In primiparous women, the prevalence of preterm birth was 5%. Underweight primiparous women using antidepressants should be closely monitored and provided tailored care in a maternity clinic.