New theories emerge on nonvertex twin delivery. (Breech Extraction may not be so Risky).

SARASOTA, FLA. -- Dogm a regarding the approach to take with a nonvertex second twin is increasingly being challenged by the evidence, Dr. Roger B. Newman said at a perinatal symposium sponsored by Symposia Medicus.

A barrage of papers from the 1960s and 1970s suggested that vaginal delivery of a nonvertex second twin was associated with higher perinatal morbidity and mortality than elective C-section in these cases. But the data, which had a vast effect on management of twin gestations, were based entirely on retrospective data, and many of the studies had insignificant statistical power, said Dr. Newman, professor and vice chairman of obstetrics and gynecology and director of maternal-fetal medicine at the Medical University of South Carolina, Charleston.

Further, up to 50% of twin gestations included in some studies were not identified until the onset of labor, and up to 25% were not identified until after delivery of the first twin--scenarios now virtually eliminated but which tend to compromise outcomes, he noted.

Since the 1980s, an increasing number of studies suggest breech extraction of the nonvertex second twin may not be as risky as previously thought. In one study of 76 nonvertex second twins delivered by breech extraction and 74 delivered by C-section, there were no significant differences in neonatal mortality or in Apgar scores.

A 1985 study suggested that concerns about the well-being of the nonvertex second twin might be isolated to very-low-birth-weight second twins. In another study--a review of 362 consecutive twin deliveries--only 4 cases of birth trauma occurred, and only 1 of those was associated with vaginal breech extraction. That baby suffered a fractured clavicle and a fractured humerus.

The most severe trauma in that study involved head entrapment leading to asphyxia and death in a second twin delivered by C-section.

"The point is that C-section out of hand is not the panacea you might hope it would be for ensuring an atraumatic delivery of a nonvertex twin B," Dr. Newman said.