Pregnancies with growth-retarded twins in breech-vertex presentation at increased risk for entanglement during delivery.

The purpose of this population based study on twins born in Sweden between 1961 and 1987 was to estimate the risk to the fetuses of becoming entangled during birth, and to identify those pregnancies with an increased risk for this rare complication. By using 3 separate questionnaires, 41 of 26,428 twin pregnancies with entanglement were identified. Twins in breech-vertex presentation (group A; 29 cases) were at significantly greater risk of entanglement (chi 2 = 168.3, p less than 0.001) than twins not in breech-vertex presentation (group B; 8 in vertex-vertex, 3 in breech-breech, and 1 in vertex-breech presentation). Known risk factors for entanglement in group A were intra-uterine growth retardation, a birth weight less than 2000 g, and antenatal fetal death. Intrapartum-neonatal mortality reached 38.9% in group A (median gestational week 36); and for group B, 8.3% (median gestational week 38). Entanglement during the study period occurred in 1 of 645 twin deliveries, on average. A vaginal delivery is proposed for women with twins in breech-vertex presentation, unless other risk factors leading to an increased risk for entanglement warrant abdominal delivery.