Second-Born Twin Has Higher Post-Delivery Death Risk
Second-born twins are twice as likely as the firstborn to die at birth or shortly after due to complications during delivery, British researchers report.
The risk -- which remains very small -- appears to be lessened when both twins are delivered by Caesarean section, the study found.
"Compared with the first twin, the second twin is more than twice as likely to die during delivery or in the first four weeks of life," said lead author Dr. Gordon Smith, the head of the department of obstetrics and gynecology at Cambridge University. "This is observed among twins born at term -- 36 weeks or later -- but not in prematurely delivered twins," he added.
The absolute risk to the second twin is still very small, about one in every 250 twin births, Smith said.
His team published its findings in the March 2 online edition of the British Medical Journal.
In the study, Smith's group collected data on twin pregnancies in England, Northern Ireland and Wales between 1994 and 2003. The researchers detected 1,377 cases of twin pregnancies where one twin died during delivery or shortly after.
The deaths were due to direct complications of birth, Smith said. These included prolapsed umbilical cord (delivery of the baby's umbilical cord occurs prior to the baby's birth), complications of breech birth, and separation of the second twin's placenta after delivery of the first twin.
"We found that the risk for the second twin tended to be less among those delivered by Caesarean section," Smith said. "This is consistent with previous studies, which had also suggested that planned Caesarean section was associated with lower risks of death and morbidity for the second twin," he said.
However, there is no information that shows directly that Caesarean section is protective, and the risk to any one twin baby remains very small, Smith said.
"Among twins born prematurely, the high risk of death due to prematurity probably masks the small additional risk of death due to complications of delivery for the second twin," the researcher added.
Whether a woman chooses to have a Caesarean delivery depends on the viewpoint of the individual woman, Smith said.
"This will involve her motivation to achieve a normal birth, her attitudes toward small risks of serious adverse events and her plans for future pregnancies. In particular, women planning many future births, and younger women, whose plans may be difficult to predict, may do better not to consider planned Caesarean section due to the effects of this on future pregnancies," he said.
One expert believes that the risk of death of the second born twin is even smaller in the United States than in Britain.
"I would hate to see this study used as an excuse to have every mother with twins have a Caesarean section," said Dr. F. Sessions Cole, the director of newborn medicine and head of the neonatal intensive care unit at St. Louis Children''s Hospital.
Cole said that most twins delivered at full term are delivered vaginally. "Having all mothers with twins deliver by Caesarean section would result in more risk to the mother than the small risks to the babies," he said.
Once the first twin is delivered, it is important to carefully monitor the second twin, Cole said. If there appears to be problems with the second twin, that baby may be delivered by Caesarean section, he noted. "That's the standard of care today."
Cole believes that the data in the study applies only to Great Britain. "There would be fewer such deaths in the United States," he said. "There is much greater monitoring attention given to the second twin in the United States, given the malpractice risk that any obstetrician faces when he or she delivers twins," he said.