Second-Twin Mortality Risk Doubles at Term


SAN FRANCISCO — Delivery-related perinatal death rates aren't higher for second twins overall, but they more than double in twins delivered at term, British study results suggest.

Gestational age and birth order of twins made a statistically significant difference in an analysis of data from national registries in England, Northern Ireland, and Wales; the data were collected between 1994 and 2003.

The study included 1,501 cases of intrapartum stillbirth or neonatal death of the second twin but not the first, Dr. Gordon C. Smith reported at the annual meeting of the Society for Maternal-Fetal Medicine.

The risk of death due to intrapartum anoxia or trauma in second twins was three- to fourfold higher at term (at least 36 weeks' gestation), compared with earlier deliveries.

Similarly, risk was found to be fivefold higher in second twins delivered vaginally at term, compared with babies delivered earlier.

No statistically significant increase in risk was seen with cesarean deliveries at term, said Dr. Smith of the University of Cambridge, England.

“Occasionally, the risk of death may be reduced by planned cesarean section” of twins, he said.

One physician in the audience bemoaned the widespread use of cesarean section for delivery of fetuses in breech position and for many other indications.

“Now every second twin at term? Where are we going to stop?” he asked.

Dr. Smith suggested that physicians should try to balance the risks of cesarean section with the potential benefits for each patient in their counseling and management of pregnant women.

It has been well known that vaginal delivery of a second twin carries increased risks because of a number of specific complications like cord prolapse or placental abruption, but data have been mixed on whether the risk of neonatal death increases.

British studies in 2002 and 2005 found an increased risk of perinatal death for the second twin, but a U.S. analysis of 300,000 twin births found no association between birth order and risk of neonatal death.

The previous studies all had fundamental flaws in their analytical approaches that undermined their conclusions, Dr. Smith said.

The present study excluded perinatal deaths due to congenital anomalies.

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