Background: Although management of twin deliveries has been a topic ofdiscussion for decades, a consensus on how to deliver twins is lacking. The objective of thisstudy was to examine short-term neonatal outcome of the second twin delivered by cesareansection after vaginal delivery of the first-born twin (combined delivery) and to identifypredictors of combined delivery. Methods: This study was a 3-year, population-based,retrospective cohort investigation of 1,254 twin births in Denmark. The twin births weredivided into three groups: vaginal deliveries, planned cesarean deliveries, and combineddeliveries. Data were extracted from medical records, a fetal medicine software program(Astraia), and the National Birth Registry. Short-term poor neonatal outcome was measuredas a 5-minute Apgar score 7, umbilical cord pH 7.10, and admission to neonatalintensive care unit for more than 3 days. Results: Vertex-nonvertex fetal presentations weremore prevalent in combined deliveries than vaginal deliveries (OR 4.4, 2.5–7.8). Nonvertexsecond twins born by combined delivery had a higher risk of Apgar score 7 and umbilicalcord pH 7.10 compared with vaginal delivery, unadjusted OR 6.2 (2.1–18), andunadjusted OR 3.9 (1.6–9.5). Prenatal ultrasound scans were evaluated in combineddeliveries, of which 48 percent were vertex-vertex at the last ultrasound scan in pregnancy(mean gestational age 34 + 0) and 37 percent were vertex-vertex at birth. Conclusions:Vertex-nonvertex presenting twins have an increased risk of combined delivery. Combineddeliveries are associated with increased neonatal morbidity for the second twin. (BIRTH 40:1March 2013)Key words: combined delivery, fetal presentation, neonatal outcome, twin deliveryManagement of twin deliveries has been a topic ofdiscussion for decades, yet the lack of randomized tri-als on the subject still leaves unanswered the questionconcerning optimal mode of twin delivery. In Denmark,there is a consensus that vaginal delivery may beattempted in women with cephalic presenting twins ofsimilar size, no contraindications to trial of labor, andno intrauterine growth restriction of one or both twins.However, controversy on mode of delivery still remainswhen the second twin presents as nonvertex.