Twin births, triplets and even premature singleton births should be excluded, as these are not a desirable outcome of IVF because of the risk of complications, argues David Healy of Monash University in Clayton.
Many people regard twins or triplets as the ideal result of IVF, providing an instant family, but these pregnancies are much riskier for both mothers and babies, and lead to a higher percentage of children with physical and cognitive disabilities(see below).
Doctors and regulatory agencies are now trying to reduce the soaring number of multiple births worldwide caused by IVF. "Multiple births are now at the highest level ever," says Suzy Leather of the UK's Human Fertilisation and Embryology Authority, which will soon restrict to two the number of embryos clinics can transfer to women under 40. "We want to make healthy single babies the ideal outcome of IVF. The goal is to prevent triplet and twin gestations."
At the moment, however, fertility clinics are usually compared on the basis of their live birth rates, the number of living babies born per transfer or per cycle.
Several governments publish tables listing such figures as a guide for would-be parents, a system that has been attacked by critics who argue that such "league tables" contribute to the rise in multiple births, because they encourage clinics to boost birth rates by transferring more embryos (New Scientist, 13 July 2002, p 4).
So Healy's team is instead proposing a universal measure based on the birth of single, full-term babies.
In principle, this should favour clinics that are technically superior, at the expense of those that try to boost their live birth rate by transferring more embryos.