The first test-tube twins, two sets of them, may be born soon in Australia. They are part of a batch of nine embryos successfully fertilized outside a body, and then implanted in a womb during experiments at St. Andrew's Hospital in Melbourne.
Dr. Carl Wood, professor of obstetrics at Monash University, and Dr. Alan Trounson of Queen Victoria Medical Center performed the experiments. In their first 60 attempts they were unable to get the embryo to "take" in the womb.But after developing new techniques last summer, they have been able to impregnate 13 women in 103 attempts since June, according to a report in the British journal New Scientist.
Some of the embryos have since aborted, but nine pregnancies remain viable and are eight to 24 weeks old. The pregnancies involving the two sets of twins are 10 and 14 weeks along.
Four test-tube babies have been born using earlier, more difficult, techniques. Wood's success in producing so many pregnancies results from two new techniques he had added to the in vitro (in glass) fertilization process.
First, he gave the women fertility drugs and controlled the timing of ovulation with hormones, which allowed him to get more eggs and get them on a schedule he set. In the four births that have resulted from in vitro fertilization, eggs have "taken" during the natural ovulation time of the mothers.
With the new technique, Wood could set the time of both ovulation and fertilization in advance, so as to catch more easily the best moment to reimplant the fertilized egg in the womb.
Other improvements were made in the process of implanting the egg in the womb.
One of the new techniques was the reason for the first test-tube twins. With the agreement of the women, the doctors now implant two embryos rather than one in order to improve the chances that one will take -- thus the high proportion of twins in the nine successful pregnancies. Of the 13 pregnancies which first appeared successful, five were twins.
In an effort to make the whole test-tube baby process easier so that clinics may readily use it, Wood and Trounso plan to try implanting embryos that have been fertilized and then frozen. This would possibly increase the chances of a successful pregnancy because surgeons would be able to perform implantation at a time when the women are not still suffering the effects of the surgical techniques used to obtain eggs.
Freezing embryos would also provide a constant supply of embryos if the procedure failed to produce a pregnancy on the first try. Frozen embryos have been successfully implanted in animals, but questions remain whether some damage to the embryos might be caused by the freezing.
Wood, Trounson, and others gave Austrailia its first test-tube baby, and since have successfully implanted another embryo by earlier methods. That baby is due in April.