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

Uncertainty and insecurity in the relationship between the mother and father of a child are responsible for heightened maternal stress, which can lead to preterm birth (PTB). Different intensities of prenatal stress (proxied by four levels of marital status linked with the presence or absence of paternal data on birth records) were defined as the Marital-Father Data index. We assessed the impact of those varying intensities of prenatal stress on PTB with respect to parity among a group of Polish mothers residing in Krakow (N = 87,916). 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). The adjusted p for the linear trend between Marital-Father Data index and PTB was less than 0.001. The adjusted effect of perceived prenatal stress differed with respect to parity (confirmed by statistically significant interactions between Marital-Father Data index levels and parity), with a higher magnitude of this effect noted among multiparous versus primiparous women. Low paternal involvement and support during pregnancy may negatively affect PTB risk and this effect may differ in relation to parity status. More attention should be paid to maternal pregnancy stress, especially of multiparous mothers, to decrease the risk of unfavorable birth outcomes.