Despite more than a decade of experience, lh< success rate of in vitro fertilization (IVF) in the United Stales, Britain, France, Australia and other major centres remains stubbornly low.

The initial birth in Singapore from fertilization outside the human body was in 1983, four years after the world's first IVE' baby was bom In Britain.

Using the standard IVF technique of mixing sperm and eggs in the laboratory be fore implanting Ihc embryo in the human womb, nearly 29 per cent of the women trealed by Ihc Singapore General Hospital's centre for assisted reproduction were able lo conceive and successfully carry their pregnancy lo full term.

But although this was one of Ihc highest rates of any country, it still means that an average of less than one tn three of the women uriable lo conceive naturally ran have a child wilh the aid of modern reprod uc-,Uvc technology.

RcMcarcb being carried out at the National University Hospital in Singapore suggests that a promising avenue for increasing ihc rale of test-tube fertilization, and then carrying ,il through Ihc full cycle of pregnancy to healthy five birth, is lo replicate a key part of the human womb In the laboratory.

In a series of experiments since 1988 that were reported in ihc British medic! journal , Human Reproduction, a Na-

tional University Hospital rc serach team headed by Arif Bongso/associate professor in the hospital's department of obstetrics and gynecology. has succeeded in cultivating cells of the fallopian lube and using them as a bed for producing succx'ssful IVF pregnancies.

Under natural conditions of human reproduction, eggs released by the ovaries into two fallopian tubes on either side of the uterus arc fertilized by sperm deep inside ihc lubes.

Five days later, a fertilized egg in embryo form emerges from one of the tubes and at laches itself to the wall of Ihc uterus to grow into a baby.

Dr. Bongso said.il appeared from research carried out by his Icam that standard IVF techniques enjoyed less than optima) success because they (ailed to replicate al (cast some o( the conditions o( the natural environment of the fallopian tube.

Within the tube, long hab like cells called cilia aid fert ization by helping lo bri g sperm up to the point wh ic they meet and penetrate eggs. The cilia then assist the < m bryo to travel down Ihc tube and enter Ihc uterus.

The shorter hairs In the fal loptan lubes, known as mi crovilli release nourishment for flic growing embryo on the downward journey as it mul-liplft s rapidly Into a more

complex cell structure.

A majority of women who turn to IVF for conception have fallopian tubes that dd not function properly, in the stan dard technology, sperm and eggs arc mixed in a liny dish containing a culture made up of a nourishing cocktail ol sails, proteins, glucose, carbohydrates and sometimes hormones.

To prevent possible premature death, the fertilized eggs are removed from the dish after only two days and placed in the uterus.

Dr. Bongso said that on average only about 25 per cent of the Iwo-day-old fertilized eggs produced in this way survive to reach the five- day stage when, under natural conditions, an embryo Travelling down the lallopiari tube would attach it self lo the wall of the uterus.

"We are trying to develop an environment outside the womb in which an embryo will grow very well lo five days old and then be placed in the uterus so that it will implant Immediately." he explained.

Dr Bongso said that there had Ixen a marked improve ment in the longevity and qual ily of fertilized eggs when they were placed on beds of fallopian tube cells. Using embryos from the same1 women, 69 per rani had reached the five-day stage of lube rail linings, compared with only 33 percent in a traditional IVF culture medium.