The Effect of Prenatal Stress, Proxied by Marital and Paternity Status, on the Risk of Preterm Birth.

We found a pattern across the adjusted risk ratios (RR) of preterm birth that ordered these estimates in an increasing trend towards higher risk, beginning with the group of married mothers with father data present (baseline), through the groups of legitimizing marriages—married after conception with father data present (RR = 1.1; 95% Confidence Intervals (CI) 1.0–1.2) and unmarried mothers with father data present (RR = 1.3; 95% CI 1.2–1.5) to the group of unmarried mothers with father data absent (RR = 1.9; 95% CI 1.7–2.2).

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