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to be associated with an increased risk of preterm birth, when we adjusted for mode of first delivery. There was a nonsignificant increase in the risk of preterm birth in those who delivered via cesarean section after a second stage of labor of ≥7 hours. 70%) of vaginal birth. A second stage of labor of ≥7 hours did not appear to be associated with an increased risk of preterm birth, when we adjusted for mode of first delivery. There was a nonsignificant increase in the risk of preterm birth in those who delivered via cesarean section