Frozen embryo babies ‘healthier’

IVF babies born from frozen embryos are heavier and result in longer pregnancies than those born from fresh embryos, research suggests.

Freezing embryos enables couples to have several cycles of IVF with eggs collected during one round of treatment. By putting some on ice, couples can use up their fresh embryos before moving on to frozen ones at a later date.

The research suggests frozen embryo transfer in IVF may lead to healthier babies, owing to a good birth weight and ability for the foetus to last the course of pregnancy.

Presented at the British Fertility Society Annual Meeting in Leeds, the study involved measuring the weight and length of gestation for 384 babies born after fresh embryo transfer and 108 born after frozen embryo transfer.

All the babies were single births, with no twin or triplet pregnancies included in the study.

Babies born from frozen embryos were, on average, 253g heavier than those born from fresh, the results showed. The proportion of low birth weight babies (weighing less than 2.5kg) was also lower in this group (3.7 per cent compared to 10.7 per cent for babies born from fresh embryos).

Frozen embryo babies typically had a longer gestation period (0.65 weeks longer) than those born from fresh embryos, the research also found.

Lead researcher Suzanne Cawood, deputy head of embryology at the Centre for Reproductive and Genetic Health, London, said: “For all assisted reproduction technologies, it is important that we ensure the procedures promote optimal health in the resulting children throughout their lives.

“Our study suggests babies born from frozen embryos have a significantly longer gestation period and are significantly heavier at birth compared to babies from fresh embryos.

In 2008, Danish scientists also found that babies born after frozen embryo transfer had higher birth weights than those born from fresh embryos. They suggested only top quality embryos survive the freezing and thawing process.

Infertility Network UK chief executive, Clare Lewis-Jones, said the new study supported the move to transferring only one embryo at a time.

This cuts down the multiple pregnancy rate – which is higher in IVF than natural conception – with health benefits for mother and baby.