Migration Background and Preterm Birth in Sweden : A multigenerational register-based cohort study

Abstract: The aim of this study was to compare preterm birth (PTB) in daughters (G2) and granddaughters (G3) of foreign- and Swedish-born women (G1), to evaluate patterns in PTB in relation to migrant background over generations. A multigenerational cohort study was conducted using register data. Two generations of women born in Sweden between 1973 and 2016 were identified. Logistic regressions were used to estimate Odds Ratios (OR) at 95%CI for PTB (<37 gestational weeks) for G2 and G3 by G1 country/region of birth (ref: Sweden). G2 daughters born to a migrant mother (G1) faced a disadvantage compared to their counterparts born to a Swedish mother. In G3, odds of PTB declined across all migrant groups revealing an advantage in some select groups relative to the Swedish reference group. The most pronounced decrease in PTB among Swedish-born women with migrant background was found in the Eastern European and Balkan (ORG2 1.55; 95%CI 1.38,1.74; and ORG3 0.85; 95%CI 0.74,0.98 respectively) and Non-Western main groups (ORG2 1.21; 95%CI 1.07, 1.37; and ORG3 0.79; 95%CI 0.68, 0.91). This study shows a decreased difference in PTB over generations among women with and without a foreign background. Further studies should determine the causes for the observed pattern.