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Single embryo transfer should be the norm say researchers

Replacing one single embryo in women should be the "gold standard" for couples undergoing fertility treatment in future, a conference on human reproduction was told today.
(Monday 28 June).

Belgian researchers found that by applying strict criteria to the quality of the single embryo they could achieve a pregnancy rate similar to normal fertile couples and, importantly, reduce the number of twins to the rate occurring normally in nature.*

"Multiple pregnancy has reached epidemic proportions since IVF and ICSI** became routine treatments worldwide", Dr Jan Gerris told a news conference at the annual meeting of the European Society of Human Reproduction and Embryology (ESHRE) in Tours, France.

A third of all IVF/ICSI pregnancies were multiple and over half of children born belonged to a set of multiples because doctors try to maximise conception chances by replacing two, three or even more embryos. Limiting the embryos to two or three has led to a decline in triplets, but not twins.

Yet even twin pregnancies can led to serious complications according to Dr Gerris. These include smaller babies, premature birth and obstetrical problems, with severe medical and psychosocial consequences and health care costs.

"It affects tens of thousands of newborns a year and despite accumulating evidence of twin pregnancy complications, the problem remains. There is pressure from patients - impatience to achieve a pregnancy and to avoid the financial burden of undergoing several cycles of treatment and there is suboptimal quality of IVF laboratories and competition between IVF centres to produce high success rates. Doctors are reluctant to replace a single embryo through fear of reducing the pregnancy rate too much."

The stumbling block up to now has been the correct identification of embryos with a high potential for implantation. But researchers at the Fertility Centre, Middelheim Hospital in Antwerp, have identified which characteristics predicted a potential implantation rate of nearly 50%. They then went on to use those criteria in a prospective randomised trial among women under 34 who were undergoing their first IVF or ICSI treatment cycle.

A total of 53 women who produced two top quality embryos were randomised to receive one or two. Out of 26 single embryo transfers, there were 10 ongoing pregnancies - a success rate of almost 40%, with one identical twin pregnancy. Out of 27 double embryo transfers there were 19 ongoing pregnancies (70%) of which there were six twin pregnancies (30%). Given this high pregnancy rate with no non-identical twins following transfer of only one embryo, it is felt that single embryo transfer should be used whenever appropriate.

About 70% of the total number of patients treated during the study period produced at least one top quality embryo, so the target group for single embryo transfer is large. The implantation rate remained the same in women up to the age of 38, although in those aged 34 to 38 somewhat fewer of the fertilized eggs developed into top quality embryos.

Dr Gerris said it should be made clear to patients and those involved in treating infertility that twin pregnancy was a relative failure - not a desirable goal.

"Single embryo transfer will progressively be considered the standard of good medical practice in all women under 38 in their first IVF/ICSI attempt. As roughly 70% of all IVF/ICSI cycles produce at least one top quality embryo, the incidence of twins can be reduced drastically, and in patients with medical reasons which forbid twin pregnancy a single embryo transfer of a top quality embryo is mandatory.

"In the future, the single embryo transfer could be extended to subsequent cycles as well as after thawing of frozen embryos, but that requires further clinical research on large numbers.

Dr Gerris concluded with a plea to governments and insurance companies. "They should fully refund IVF/ICS treatment. That will lead easier acceptance of single embryo transfer and to substantial savings in antenatal and neonatal costs."

*A pregnancy rate of 25-30% per menstrual cycle is the norm for fertile couples. The natural incidence of twins is under one per cent.
**IVF (in vitro fertilization): fertilization of an egg by sperm in a laboratory dish.
ICSI (intracytoplasmic sperm injection): process by which an egg is fertilized by injecting a single sperm into the egg.
Abstract no: O-015

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