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Purpose Previous research suggests that job loss in a household during pregnancy may perturb fetal growth. However, this work often cannot rule out unmeasured confounding due to selection into job loss. Recent work using data on exogenous job loss (due to a plant closure) finds that a father's unexpected job loss during his spouse's pregnancy increases the risk of a low weight birth. Using a unique set of linked registries in Denmark, we build on this work and examine whether associations between a father's unexpected job loss and low birthweight differ by trimester of in utero exposure. We additionally examine trimester-specific associations of job loss with small-for-gestational-age, a proxy for restricted fetal growth, which may cause low birthweight. Methods We apply a sibling control design to over 1.4 million live births in Denmark, 1980 to 2017, to examine whether this plausibly exogenous form of job loss corresponds with increased risk of low weight or small-for-gestational-age births, depending on the timing of displacement in the first, second, or third trimester. Results Results indicate an elevated risk of low birthweight (OR = 1.80, 95% CI: 1.24, 2.62) and small-for-gestational-age (OR = 1.40, 95% CI: 1.02, 1.93) among gestations exposed to job loss in the second trimester of pregnancy. Sensitivity analyses using continuous outcome measures (e.g., birthweight in grams, birthweight for gestational age percentile) and maternal fixed effects analyses produce substantively similar inference. Conclusions Findings support the notion that unexpected job loss may affect fetal growth and that the second trimester in particular appears sensitive to this external stressor., Purpose: Previous research suggests that job loss in a household during pregnancy may perturb fetal growth. However, this work often cannot rule out unmeasured confounding due to selection into job loss. Recent work using data on exogenous job loss (due to a plant closure) finds that a father's unexpected job loss during his spouse's pregnancy increases the risk of a low weight birth. Using a unique set of linked registries in Denmark, we build on this work and examine whether associations between a father's unexpected job loss and low birthweight differ by trimester of in utero exposure. We additionally examine trimester-specific associations of job loss with small-for-gestational-age, a proxy for restricted fetal growth, which may cause low birthweight. Methods: We apply a sibling control design to over 1.4 million live births in Denmark, 1980 to 2017, to examine whether this plausibly exogenous form of job loss corresponds with increased risk of low weight or small-for-gestational-age births, depending on the timing of displacement in the first, second, or third trimester. Results: Results indicate an elevated risk of low birthweight (OR = 1.80, 95% CI: 1.24, 2.62) and small-for-gestational-age (OR = 1.40, 95% CI: 1.02, 1.93) among gestations exposed to job loss in the second trimester of pregnancy. Sensitivity analyses using continuous outcome measures (e.g., birthweight in grams, birthweight for gestational age percentile) and maternal fixed effects analyses produce substantively similar inference. Conclusions: Findings support the notion that unexpected job loss may affect fetal growth and that the second trimester in particular appears sensitive to this external stressor.

BACKGROUND: Research documents social and economic antecedents of adverse birth outcomes, which may include involuntary job loss. Previous work on job loss and adverse birth outcomes, however, lacks high-quality individual data on, and variation in, plausibly exogenous job loss during pregnancy and therefore cannot rule out strong confounding.METHODS: We analysed unique linked registries in Denmark, from 1980 to 2017, to examine whether a father's involuntary job loss during his spouse's pregnancy increases the risk of a low-weight (i.e. <2500 grams) and/or preterm (i.e. <37 weeks of gestational age) birth. We applied a matched-sibling design to 743 574 sibling pairs.RESULTS: Results indicate an increased risk of a low-weight birth among infants exposed in utero to fathers' unexpected job loss [odds ratio (OR) = 1.37, 95% confidence interval (CI): 1.07, 1.75]. Sex-specific analyses show that this result holds for males (OR = 1.70, 95% CI: 1.14, 2.53) but not females (OR = 1.24, 95% CI: 0.80, 1.91). We find no relation with preterm birth.CONCLUSIONS: Findings support the inference that a father's unexpected job loss adversely affects the course of pregnancy, especially among males exposed in utero.