Birth order and delivery interval: Analysis of twin pair perinatal outcomes

Objective. To determine whether second-born twins ( B) have higher morbidity and mortality than first-born twins ( A), using a paired analysis. Study design. We conducted a retrospective analysis of birth certificates and fetal and infant death certificates for 5138 twin pairs selected from those born in Washington State from 1989 to 2001. Twin A was vertex and delivered vaginally. Pairs were not size-discordant (<20%) and had no malformations. Matched-pair odds ratios were calculated. Results. Twin B had more fetal distress (OR = 6.0) and more low 5-min Apgar scores ( OR = 2.1) than Twin A, except at short delivery intervals. Pairs had relatively high rates of combined vaginal plus cesarean deliveries at delivery intervals >= 15 min. Conclusion. If prompt vaginal delivery of Twin B does not occur, the benefits of vaginal delivery for Twin A might not outweigh the risks of distress and low Apgar scores in Twin B and vaginal plus cesarean delivery for the mother.