The relationship between inter-twin delivery interval and metabolic acidosis in the second twin

Abstract

To investigate the relationship between inter-twin delivery interval (ITDI) and metabolic acidosis in the second twin at birth. Retrospective cohort study in a tertiary-level teaching hospital. Twins with birth weights > 750g and vaginal delivery of the first baby were identified from an obstetrical database over a 10 year period. Mean arterial cord pH, and base deficit among different ITDI were calculated by analysis of variance. Logistic regression models were used to estimate effects of ITDI on metabolic acidosis. The main outcome measure was the incidence of metabolic acidosis in the second twin (defined as pH < 7.0 and base deficit > 12 mmol/L) at different ITDI. 310 twin pairs met the inclusion criteria. Second twin mean pH was significantly lower and base deficit significantly higher when ITDI exceeded 60 minutes. The incidence of metabolic acidosis increased with increasing ITDI (chi square test for linear trend p=0.02) and at > 60minutes there was a substantially greater proportion (3/9) of acidotic neonates when compared to ITDI of < 15 minutes [OR=22.6 (95%CI 2.5, 494.1)] An ITDI of 60 minutes is a reasonable time threshold at which to consider operative delivery. The application of such a policy for the 8% of second twins in our population, who exceeded this 60 minute interval, could result in a 33% reduction in the number of babies exposed to the potentially damaging effects of metabolic acidosis.