Twins tend to do better if born vaginally, rather than by caesarean section, researchers report in the online paper BJOG. But regardless of delivery mode, the first-born twin is less likely to suffer complications than the second.
As Dr A. Cristina Rossi said, "My review shows that the first twin is less likely to experience adverse outcomes compared with the second co-twin. Vaginal delivery seems to be safer for the first twin than caesarean section."
Dr Rossi of San Giacomo Hospital, Monopoli, Bari, Italy, and colleagues conducted a systematic review and meta-analysis, involving 18 studies, 12 of which reported neonatal outcomes for both twins. In all studies, both twins were alive during labour and outcomes were stratified for birth order and presentation, as well as planned and actual delivery mode.
39,000 twins involved
Neonatal morbidity was lower in the first than the second twin (3.0% versus 4.6%). This was also true of mortality (0.35% versus 0.6%).
In either twin there were no differences between vertex and non-vertex and attempted vaginal delivery versus planned caesarean section.
In the first twin, neonatal morbidity was lower after vaginal delivery than caesarean section (1.1% versus 2.1%).
When the first twin underwent vaginal delivery and the co-twin underwent caesarean section (combined delivery), morbidity was significantly higher in the co-twin (19.8%) than in the case of vaginal delivery (9%) or caesarean delivery of both newborns (7.2%).
"In the absence of more definitive data, our systematic review suggests that an attempt at vaginal delivery should be considered in twin pregnancies," say the investigators.
"With regard to the second twin, no differences are noted between caesarean section and vaginal delivery. Therefore, when the twins are both in vertex presentation, vaginal delivery can be attempted," added Dr Rossi.
"If there is a vertex presentation of the first twin and non-vertex presentation of the second, women should be advised that trial of labour may be a safe option in the absence of risk factors for combined delivery."
"However, predicting combined delivery in the antenatal period can be very difficult," she concluded.
(Reuters Health, David Douglas, February 2011)