Current practice for most In vitro fertilisation (IVF) clinics is that the best, fresh embryos are used first and only spare, good-quality embryos are frozen for transfer at a later stage.
Researchers from the University of Aberdeen systematically reviewed more than 37,000 IVF pregnancies and found that there was a reduced chance of mothers bleeding and of babies being born prematurely with low birth weight when the embryos were stored and frozen compared with treatment involving freshly-transplanted ones, The Independent reported.
The review of 11 international studies also found that the death rate immediately before and after birth was lower in babies who were born as a result of transferring frozen-thawed embryos into the womb compared with the transfer of fresh IVF embryos.
Scientists said the results should reassure mothers who intend to have IVF treatment with frozen embryos, but opinions are divided about whether the findings should lead to a change in the existing policy.
"If pregnancy rates are equal and outcome in pregnancies are better, our results question whether one should consider freezing all embryos and transferring them at a later date, rather than transferring fresh embryos," lead reseracher, Abha Maheshwari, said.
"This represents a major paradigm change in assisted reproduction, and one which could satisfy the twin demands of optimising safety and success. Traditionally it has been thought that fresh is always better and used as a first choice," Maheshwari was quoted as saying by the paper.
"Initially there were concerns about the safety of freezing techniques, and it was felt the quality of the embryo could deteriorate and impact on the health of the child. However, data to date has been reassuring," Maheshwari told the British Science Festival in Aberdeen.
The study was published in journal Fertility and Sterility.