Frozen embryo babies just as healthy: researchers

BARCELONA (Reuters) - Babies born from frozen embryos weigh more, have no greater risk of birth defects and are as healthy or healthier than those conceived using fresh ones, Danish researchers said on Tuesday.

Their findings, presented at a meeting of the European Society of Human Reproduction and Embryology, provided some of the strongest evidence yet that freezing and thawing embryos for in vitro fertilization poses no increased risk for a child.

"Up until now the data has been extremely limited," Anja Pinborg, a researcher at the Copenhagen University Hospital Rigshospitalet in Denmark, told reporters. "We wanted to be sure that the procedure had no deleterious effect on the offspring."

The technique, in which embryos are frozen until they can be implanted in the mother, helps to reduce the number of times a woman has to undergo a procedure to collect eggs.

It is important because of a push among governments and the medical community away from transferring multiple eggs at the same time, which boosts the chances of pregnancy but increases the risk of complications.

"If our results continue to be positive, frozen embryo replacement can be accepted as a completely safe procedure, which can be used even more frequently than it is currently," Pinborg said.

The scientists studied all 1,267 children born in Denmark between 1995 and 2006 using frozen embryos and compared them with nearly 18,000 children born from fresh embryos during the same period.

Data from Danish national registries showed babies in the frozen embryo group weighed about 200 grams more at birth, while the percentage of pre-term births and low birth weight children was lower, the researchers said.

They found no increased risk of congenital birth defects among babies born from frozen embryos and fewer of these children spent time in neonatal intensive care units.

"According to this study, which is currently the largest on frozen embryo replacement offspring, these children perform as ... offspring after fresh embryo transplant or even better," the researchers said in their study.

The researchers added that they did not believe freezing improved a baby's chances. Instead, an explanation might be that only the strongest embryos survived the freezing process.

(Reporting by Michael Kahn; editing by Maggie Fox and Andrew Dobbie)