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Freeze, thaw and mate-a rare baby
By Tonny Chan (China Daily HK Edition)
Updated: 2004-08-07 10:17
Scientists from the Assisted Reproduction Technology (ART) team of Chinese
University of Hong Kong (CUHK) were more than jubilant when they witnessed the
birth of a 3.14-kilogram baby at the hospital on April 29 this year.
The boy, whose identity has been withheld by ART, is Hong Kong's first baby
involving a frozen-and-thawed human egg inseminated by frozen-and-thawed sperm.
The researchers are still checking global scientific journals to see if he is
the first of his kind in the world.
The boy's mother is a 37-year-old woman with a five-year history of tubal
occlusion (blockage), according to Tony Chiu, an honorary assistant professor in
the Department of Obstetrics and Gynaecology at CUHK.
She went to the Prince of Wales Hospital, the university's study hospital,
for her first in-vitro fertilization (IVF) treatment in March last year.
However, the husband - probably because of stress - failed to produce a semen
sample while 23 eggs were smoothly extracted from the woman.
Unless the eggs were frozen, the woman would have had no choice but to go for
another collection that Chiu said would have involved a certain risk.
The couple chose to have the eggs frozen and the road to making history thus
began.
Chiu said the husband, after his stress reduced, produced a semen sample
three months later which was frozen.
What followed was a complicated process of thawing, insemination and
blastocyst (a cluster of cells prior to the embryo stage) nurturing in the
laboratory until two blastocysts were implanted in the mother. One of them
withered but the other continued to grow and eventually led to the birth.
Chiu said it was a significant breakthrough because it involved the
application of three assisted-reproduction techniques in one single case - the
freezing and thawing of human eggs and sperm; and the nurturing of blastocysts.
Citing documented records, he said there were fewer than 70 births involving
the use of frozen eggs in the world during the past 15 years.
None, as far as he could recall, involved the successful application of the
three techniques at the same time.
Chiu explained that it was difficult to achieve successful pregnancy from the
use of frozen eggs. Statistics gathered by ART since its human-egg freezing
programme began in 1999 reveal a successful rate of only one in 73.
Cheung Lai-ping, honorary clinical associate professor at the same
department, said it remains unclear how far the steps of freezing, thawing,
dehydrating and hydrating possibly impair the chromosomes in the cell but the
risk is clear.
Theoretically, anyone who cannot conceive because of health reasons or
through ordinary IVF procedures could benefit from the egg-freezing technology,
Cheung said.
But he warned that there was still a long way to go before it could be
meaningfully applied to cancer patients because there were documented cases of
residual cancerous cells in the mother finding their way to the embryos.
Until an answer is found to the risk, the benefits remain hypothetical for
cancer patients, according to Cheung.
Chiu said the Assisted Human Reproduction Unit at the Prince of Wales
Hospital offered the egg-freezing service to couples only when no sperm was
available on the day of egg collection.
Since 1999, 85 eggs from 12 women have been frozen and 73 of these frozen
eggs from 11 patients have been thawed for insemination. But only one of the 73
thawed eggs led to the birth on April 29.
"The baby is healthy. That's all I can say," Chiu said.
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