Outcomes Similar for Kids of Fresh or Frozen Embryos

Children born from frozen embryos in assisted reproduction have outcomes similar to children born from fresh embryos, researchers have found.

In a meta-analysis, researchers found no difference in rates of preterm birth, low birthweight, or malformations between kids born from frozen or fresh embryos, Ulla-Britt Wennerholm, M.D., of East Hospital in Goteborg, Sweden, and colleagues reported online in Human Reproduction.

"Some of these large-registry studies show even better outcomes for the frozen embryos in terms of preterm birth and low birthweight," Dr. Wennerholm said.

She said a growing proportion of assisted reproductive technologies use cryopreservation of embryos. The two technologies are slow freezing, -- which is more popular -- and vitrification, or flash-freezing.

Besides embryos, blastocysts and oocytes are also being frozen more often, she said.

Note that the study concludes more research is needed on the cryopreservation techniques regarding blastocysts and oocytes.

One of the biggest concerns in assisted reproductive technology has been the health of the children born, Dr. Wennerholm said.

So the researchers conducted a systematic review of about 20 studies of in-vitro fertilization or intracytoplasmic sperm injection using either fresh or frozen embryos.

For embryos in the early cleavage stage, the researchers found comparable, if not better, rates of preterm birth and low birthweight for those born after cryopreservation and those born after fresh cycles.

For singletons, preterm birth rates varied between 9.2% and 12% in the frozen embryo group, and between 7.4% and 14% for the fresh embryo group.

In two studies, however, the preterm birth rate in singletons was significantly lower for children born of frozen rather than fresh embryos, but there was no significant difference between the two in other studies.

For twins, preterm birth rate in frozen embryos varied between 33% and 62%, compared with 47.6% and 61.3% for fresh-embryo twins.…Read more

Source: MedPage Today