Objectives. To compare perinatal and infant mortality in breech and cephalic presentations and between planned vaginal and cesarean section (CS) breech deliveries in Sweden.
Methods. The study comprised two parts. Study A is a national cohort study for the period 1991–2001, including 22 549 breech presentations and 875 249 cephalic presentations born at ≥38 completed weeks. Study B is a case–control study, including all 164 breech deliveries with perinatal or 1-year infant death (during 1991–1999 in Sweden) and controls.
Results. Study A: Among non-malformed infants, the total mortality rate was 0.46% in breech and 0.28% in cephalic presentations [adjusted odds ratio (OR) 1.6; 95% confidence interval 1.3–1.9]. Non-malformed breech babies were at an increased risk of antenatal death (breech versus cephalic hazard ratio: 2.7, 2.1–3.6). The infant mortality among non-malformed breech deliveries was higher in vaginal birth than in delivery by CS before labor (OR 2.5, 1.2–5.3). The perinatal + infant mortality among non-malformed breech babies was higher at delivery after 39 completed weeks than at CS delivery at 38 weeks (0.53% versus 0.14%; OR 3.5, 1.9–6.4). The estimated needed number of CS to avoid one death was 400. Study B: In breech presentations without malformations, OR for perinatal or infant death was 3.1 (1.7–5.8) at planned vaginal delivery compared with planned CS delivery, and when breech presentations not diagnosed at 37 gestational weeks were excluded, OR was 3.7 (1.6–9.2).
Conclusions. These large population-based and case-control studies both show a significant reduction of perinatal and infant mortality with planned CS in term breech pregnancy.