Benefits of frozen IVF embryos highlighted

CURRENT BEST practice in the preparation of embryos for in-vitro fertilisation may be wrong and may have to change.

New research shows both the mother and the infant do better if the embryos used have been frozen and then thawed prior to implantation in the mother’s womb.

The assumption has been that it was always better to use a fresh embryo rather than a stored embryo, said Dr Abha Maheshwari, senior lecturer at the University of Aberdeen and consultant in reproductive medicine with UK National Health Service Grampian.

Research has shown that foetuses developing from previously frozen embryos stood less of a chance of being born early and at low birth weight, while the mother experienced less bleeding during the pregnancy.

Dr Maheshwari’s findings are presented this morning on the opening day of the British Science Association’s annual Festival of Science, taking place this year at the University of Aberdeen. They have also just been published in the journal Fertility Sterility.

He and his research team had looked at 11 international published studies involving more than 37,000 pregnancies following implantation of either a fresh or a thawed frozen embryo.

“We found pregnancies arising from the transfer of frozen thawed embryos seem to have better outcomes both for mums and babies when compared to those after fresh embryo transfer,” he said. The assumption had been that “fresh is always better”, with fresh embryos used as a first choice.

Doctors working in the field have traditionally tried to increase the chances of implantation and a successful pregnancy by introducing several embryos into the womb, with a higher than usual multiple birth rate when using these techniques.

Over time, however, there has been a move to single embryo transfer, backed by the UK’s Health and Fertilisation and Embryology Authority.

It has still been the practice, however, to extract several eggs at the same time, leading to the increased use of freezing to preserve viable embryos, said Dr Maheshwari. “If pregnancy rates are equal and outcome in pregnancies are better, our results question whether one should consider freezing all embryos and transfer them at a later date, rather than transferring fresh embryos,” he said.

He noted the existing data had limitations, and larger studies were needed before any change in best practice was introduced.

Meanwhile, attendees at the festival heard yesterday of advances in silicon chip technology that have the potential to make phones and computers effectively unhackable. Scientists at the University of Bristol’s Centre for Quantum Photonics announced a chip that can be mass-manufactured and which works not by channelling the movement of electrons through its circuits, but the transfer of light particles or photons.

The prototype devices were 1,000 times smaller and more complex than current technologies, said Prof Mark Thompson, deputy director of the centre. The full chip is only two by four millimetres and the circuits handling the photons are only several hundred-millionths of a metre across.

The Festival of Science is an annual celebration of science that typically attracts 50,000 people, including 10,000 schoolchildren. Those attending will be able to choose from 200 different events involving 350 international scientists at the six-day event, which runs until September 9th.

The Irish Times will be providing daily coverage from the event until Saturday.