The risk of fetal death in twin pregnancies is higher than previously estimated, a new study from the UK finds. The researchers suggest this danger could be eliminated by planning to deliver the babies by c-section at 32 weeks.

Dr. Nicholas M. Fisk of Imperial College London and colleagues have observed unexpected late fetal deaths in apparently uncomplicated twin pregnancies. This prompted them to conduct the current study, to investigate the risk of such deaths after 24 weeks gestation.

The researchers evaluated records at their center for 480 twin pregnancies in which the babies shared a single chorion membrane. The mothers underwent ultrasound monitoring every two weeks.

The team identified 151 uncomplicated pregnancies, with normal ultrasound scans, but among this group there were ten late unexpected fetal deaths in seven pregnancies - three double deaths and four single deaths.

All the fetal deaths occurred within 2 weeks of a normal scan, at an average gestational age of 34 weeks, the investigators report in the journal PLoS Medicine. The deaths remained unexplained after autopsy in three of the five pregnancies; in two there was evidence of a condition called twin-twin transfusion syndrome, which can arise when twins share one chorion membrane.

Strategies to prevent these late fetal deaths could include more intensive monitoring, Fisk and his colleagues recommend, or earlier elective delivery. Because most of the fetal deaths occurred after 32 weeks, they suggest scheduling elective delivery at this point in the pregnancy.

“If our findings are confirmed in other observational series,” the researchers conclude, “our suggestion that earlier delivery might prevent this adverse outcome could be tested by randomized trial.”

SOURCE: PloS Medicine, June 2005.