Scientists looking at in-vitro fertilization now say doctors should limit the number of embryos they implant to one or two.
The study, published in The Lancet, shows the rate of live birth is greater when the mother is implanted with one or two embryos as opposed to three or more.
Implanting three or more embryos was associated with a high risk for severe preterm birth.
Copyright 2012 KPHO (Meredith Corporation). All rights reserved. CBS News contributed to this report.