If the first child is breech, overall outcomes for families with two children are similar regardless of the mode of the first birth.

Cesarean section for breech presentation is often recommended. However, cesarean section affects future reproduction. The aim of this study was to assess the effect of mode of the first birth in breech on outcomes of the second birth and the two births together. This is a register-based nationwide cohort study including 23 062 women with a first singleton birth in breech ≥ 34 gestational weeks and a subsequent singleton birth in Sweden 2000-2019. Exposure was mode of first delivery. Main maternal outcome was a composite of fourth-degree perineal injury, postpartum hemorrhage requiring blood transfusion, hysterectomy, or death. Main infant outcome was a composite of stillbirth, extremely preterm birth (< 28 weeks), moderate to severe hypoxic ischemic encephalopathy, therapeutic hypothermia, or death. Outcomes were analyzed using multivariable logistic regression. In the first birth, the infant composite outcome affected < 1% in both groups but the risk was higher in the vaginal breech group (13/1525), compared with the breech CS group (27/21 537), aOR 7.06, 95% CI 2.91-17.1. In the second birth, the infant composite outcome affected < 1% in both groups but the risk was lower for the first vaginal breech group (3/1525) compared with the first breech CS group (152/21 537), aOR 0.26, 95% CI 0.08-0.84. There was no significant difference between the groups in risk of composite infant outcome in the two births assessed together, or in risk of composite maternal outcome. In total, the chance of a two-children family without maternal or infant severe adverse composite outcome was high and similar regardless mode of the breech first birth.