While several studies have found that twin pregnancies result in higher live birth rates, the concept of "embryo assistance" -- still entirely theoretical -- met resistance from one expert not involved in the new study.
"The authors have offered an interesting hypothesis," Dr. Alan B Copperman, director of reproductive endocrinology at Mount Sinai School of Medicine in New York, told Reuters Health by email.
"But their data are not sufficient to overturn our current understanding that embryo implantation is independent, and we do not have evidence that individual embryos 'help each other' implant."
Babies conceived through IVF account for just one percent of U.S. births each year, researchers say, but the technique is responsible for 17 percent of twins.
Doctors often [transfer] more than one embryo to increase the chances of a successful pregnancy, a practice that's particularly common in the U.S.
But given that multiple pregnancies carry risks for the fetuses, clinics have recently been cutting back on the number of embryos they transfer into women.
The American Society for Reproductive Medicine recommends that no more than two embryos should be implanted in women under 35 -- and doctors should consider using just one.
Image: Dividing cells, via Shutterstock.