"The presence of one embryo does not affect the development of its twin". So suggests a Brief Communication in this week's Nature (Vol. 416, No. 6877, 14 Mar 2002). In a group of women who released two eggs at once, the probability of both eggs becoming fertilized and developing successfully is the same as for a single egg release: 20–30%.
The prevailing view is that losses of the second fertilized egg are high very early in pregnancy, and that for every liveborn twin pair, there are 10–12 more that end in a single birth. The study casts doubt on, but does not rule out, the possibility that both twins might be lost at a higher rate than singletons.
Steven Tong of Monash University, Victoria, Australia, and colleagues used ultrasound to follow 504 pregnancies, 48 of which started in double ovulation. "The presumption of huge losses of dizygotic twins in early pregnancy is unfounded," they conclude.
tel +61 3 9594 5362,
(C) Nature press release.
Message posted by: Trevor M. D'Souza