Making babies: how far do we go?

A new fertility process offers older women a better chance of a baby. KATHERINE HOBY examines the implications.

A new embryo testing scheme that could increase pregnancy rates for older women poses all sorts of ethical questions.

Fertility Associates, based in Auckland, wants to introduce a screening process that will separate healthy embryos from those unlikely to develop into viable pregnancies through the in-vitro fertilisation (IVF) programme.

The screening process, which is used in many other countries, is called FISH - fluorescent in-situ hybridisation.

On Monday, the Ministry of Health national ethics committee gave interim approval for a feasibility study to find how successful the screening programme would be.

What does the current in-vitro fertilisation programme involve?

Sperm from the would-be father and eggs from the would-be mother are gathered and combined in a dish in an incubator.

The tiny embryo starts as one cell and then starts dividing. It keeps doubling as it develops further into an embryo. After three days it is made up of eight cells.

Embryos are then monitored and selected by doctors or scientists for placement inside the woman's uterus. Normally two are chosen for placement.

Now they are chosen by looking at the rate of development and how symmetrical they are. It is hoped a viable pregnancy will then form from one.

After five or six days in the uterus, the embryo should hatch out of its eggshell. All going well, it implants itself in the lining of the uterus and starts feeding and growing. Ten days after the embryos are implanted, there should be some sign of a pregnancy visible through a blood test.

How would the FISH process differ?

Eggs would be removed from a woman's body as part of a normal IVF cycle. The embryos would be allowed to develop for three days as before.

Cells would then be taken from the embryos and put on a slide. A DNA probe is laid against a single cell.

A microscope is used to watch for different-coloured chromosome markers to show up. Some are obvious - three chromosome 21s means a Down's Syndrome baby. There are others which are lethal to an embryo.

"What is comes down to," says Dr Bert Stewart of Fertility Associates, "is that we can see which embryos, if placed, should have a positive outcome."

The results from the embryos are then given to the prospective parents and they decide which to implant, which to freeze (if any) and which to discard.

The couple are shown slides of the embryos under a microscope and have everything explained to them.

Who is likely to get the most benefit from FISH?

It would be particularly helpful to older women. It is a biological fact that the number of eggs produced and the quality of those eggs deteriorate with age.

No one seems sure why, although two theories prevail. One is that the best oxygen-fed eggs are used first when a woman is younger. The other is that the eggs just naturally slowly deteriorate over time.

Dr Stewart says there is a gradual reduction in a woman's fertility until the age of about 38, when it drops right off.

A similar programme in the United States has doubled the chances of pregnancy for women in their late 30s to early 40s.

What benefits would it have for couples using IVF

Couples could tell which embryos were not likely to be viable and therefore avoid the present "hope for the best" approach - plus the possibility of a miscarriage or that none of the embryos would "take."

A miscarriage occurs when there are too many or not enough chromosomes in an embryo. The embryo does not develop as it should. In some cases, the body simply rejects it.

Being able to tell earlier on which embryos had the best chance would also reduce the number of emotional and expensive ($4500 each) IVF treatment cycles.

Dr Stewart says it will also prevent couples having to make difficult decisions once the embryo is already established, for example finding out a baby will have Down's Syndrome at the 15-week amniocentesis stage. Amniocentesis is a test on a sample of the fluid surrounding the foetus.

How long is one IVF cycle?

A woman starts a cycle of fertility drugs, usually on the first day of her menstrual cycle. The drugs, taken for 12-14 days, stimulate the ovaries to produce eggs.

A day and a half later, eggs are removed and combined with sperm. The IVF process begins and usually takes three weeks for older women.

What are the other issues to be considered if FISH is introduced?

Dr Stewart acknowledges that couples would be likely to need counselling.

"They would have to consider the pros and cons, and have to be counselled to cope with the possibility of a negative result, like if all the embryos are found to be unlikely to become viable."

He says prospective parents will have difficult choices to make, especially those who consider that anything that is alive is sacred.

The couple will have to have made their choices well before results come back as the embryos must be replaced within a strict time frame.

"We don't want people making decisions then, on the spot. There are a lot of issues to be considered ... a lot of what ifs."