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The future of babymaking
By Jacqueline Stenson
MSNBC CONTRIBUTOR July 22, 2003
Scientists explore new techniques for tackling
infertility problems
July 22 — Just
a few decades ago, it seemed pretty far-fetched to think
that postmenopausal women could ever bear children or that
sterile men might fertilize eggs with sluggish sperm. But
researchers have overcome these and other medical challenges
in the quarter-century since the birth of ‘test-tube’ baby
Louise Brown, a landmark event that brought the promise of
parenthood to millions of infertile couples. So what will
the future of fertility hold?
Transplanted wombs? Immortal eggs? Cloned babies?
SINCE BROWN was born in
July 1978, doctors have been steadily tweaking fertility
techniques — and boosting their effectiveness.
“The field has come a long way,” says Dr. Richard
Paulson, director of reproductive endocrinology and
infertility at the University of Southern California in Los
Angeles.
Success rates for in vitro fertilization procedures,
in which egg and sperm cells are combined in a lab dish, and
other variations of assisted reproductive technology are at
an all-time high. In 2000, the latest year for which U.S.
statistics are available, about 25 percent of treatment
cycles involving a woman’s own eggs resulted in a live
birth.
Doctors attribute improved success rates to such
factors as better culture media — the fluid that embryos are
bathed in at the lab — and the ability to grow many embryos
for as long as five days before transfer to the uterus, up
from two or three days in the past.
SELECTING
BETTER EMBRYOS
To boost birth rates higher, scientists are working
to perfect current methods as well as develop new ones. One
area of research is the development of better techniques to
identify which embryos are the best candidates for transfer
to a woman’s uterus.
Some doctors currently use a screening method called preimplantation genetic diagnosis, or PGD, which involves
removing a single cell from an embryo and testing it for
genetic defects.
The approach can be
beneficial for women who suffer repeat miscarriages due to
chromosomal abnormalities, but doctors say it has not proven
its worth as a routine screening technique for all patients.
Among its drawbacks, PGD can damage embryos and may
not always give accurate results because one cell does not
necessarily reflect the health of the entire embryo,
according to Paulson. An improvement, he says, would be a
noninvasive test that would provide more precise
information, perhaps using a special microscope.
“The principle of PGD — testing the embryo to see
whether the DNA is right or wrong — is clearly the way of
the future,” says Paulson.
PGD is also being used increasingly with some fertile
couples to screen embryos for genetic conditions, such as
cystic fibrosis and Huntington’s disease. But, even if these
diseases can be identified, experts say they’re still a long
way from being able to “fix” embryos by altering their DNA.
Some researchers also fear PGD will be used to create
“designer babies” with specific traits that have nothing to
do with their health. The technology is already being used
in some cases solely to choose a child’s sex.
“When does it stop being a medically oriented
procedure?” asks Dr. Randy Morris, an associate professor of
reproductive endocrinology at the University of Illinois in
Chicago.
“Do sex now, and eye color and free-throw-shooting ability
later? Whether society will tolerate that remains to be
seen,” says Morris.
SLOWING THE
BIOLOGICAL CLOCK
Another major goal of researchers is to figure out
how to preserve a woman’s fertility, which begins a nose
dive in her mid-30s. Scientists are trying to understand why
eggs deteriorate and how to thwart the process.
While doctors
have long been attempting to freeze eggs so that a young
career woman, for instance, could save them for use later in
life, the process is not very successful because the eggs
are so fragile, says Dr. Michael Soules, director of
reproductive endocrinology and infertility at the University
of Washington in Seattle.
“It’s not good enough to be attractive,” he says.
One approach that may make egg freezing more successful is
in vitro maturation, in which immature eggs are extracted
from the ovaries and matured in the lab. Immature eggs seem
to survive freezing better than mature eggs, raising the
possibility that doctors may one day harvest and freeze the
immature eggs and then thaw and mature them when a woman is
ready to start a family.
The benefit of in vitro maturation in routine ART is
that it prevents women from having to undergo hormone
injections to stimulate their ovaries to release multiple
mature eggs. The technique has already been used to conceive
some children but is still being investigated.
EGGS IN ABUNDANCE
Other high-tech tinkering may
one day allow for an abundant supply of new eggs or the
rejuvenation of old ones. Scientists, for instance,
have coaxed embryonic stem cells from mice to morph into
eggs in the lab. If the feat could be replicated in
humans, it might offer an alternative for infertile couples
who would otherwise need to rely on donor eggs, which may be
in short supply.
Other
investigators have proposed a technique that involves taking
the nucleus from an infertile woman’s adult cell, such as a
blood or skin cell, and putting it into a hollowed-out egg
from a donor. The goal is to create an egg that has the
genetic material of the infertile woman and is healthy
enough to be fertilized with her partner’s sperm.
But
experimentation with this technique and another approach
called cytoplasmic transfer, both of which involve genetic
manipulation beyond the direct union of egg and sperm, were
halted by the Food and Drug Administration in 2001, pending
agency approval.
During cytoplasmic transfer, cytoplasm — the part of
the cell outside of the nucleus — from a healthy donor egg
is injected into an egg of an infertile woman in an effort
to make her egg healthier. Babies have already been created
with the technique and, because cytoplasm contains small
amounts of genetic material, the kids have been shown to
have DNA from three genetic parents — two moms and a dad —
raising red flags with the FDA.
TRANSPLANTED OR
ARTIFICIAL WOMBS?
Science may also have something new in store for
women who are born without a uterus or who must have it
removed for health reasons — uterine transplants.
Doctors in Saudi Arabia say they’ve transplanted a
uterus into a woman but it had to be removed after a few
months because of blood-clotting problems. Other researchers
in Sweden have performed uterus transplants in mice, which
were then able to give birth.
Since the ideal donor would be a close genetic match,
such as a mother or sister, the ability to perform uterine
transplants might actually make it possible for a woman to
give birth from the same uterus she was born from.
Uterine transplants would offer an alternative to
surrogacy but, on the downside, would require patients to
take anti-rejection drugs to prevent their immune systems
from attacking the organ.
Taking things even further, if embryos can be created
outside the womb, why can’t the fetus develop there, too,
eliminating the need for a uterus altogether?
Experts say the ability to fertilize and grow an
embryo outside the human body for a few days has been an
amazing achievement, but one that would pale in comparison
to being able to nurture a fetus to term in the lab.
“We’re just excited we can grow the embryo to day 5,”
says Dr. Sherman Silber, director of the Infertility Center
of St. Louis at St. Luke’s Hospital. “Artificial womb — I
just don’t see that happening.”
CLONING
CONUNDRUM Meanwhile, as researchers develop new fertility
techniques, the debate over human cloning continues to rage.
Amid all the
ethical and moral concerns, fertility specialists are
skeptical human cloning would ever really be a practical —
or desirable — option for infertile couples. But experts aren’t saying that it necessarily can’t
be done.
“It’s possible, if you go by all the different
animals that have been cloned,” says Soules.
But based on the
animal experiments, scientists have learned that cloning
efforts fail the vast majority of the time and are plagued
by high rates of birth defects and other problems. In
addition, no primates have ever been successfully cloned.
So what about those recent cloned-baby claims by Clonaid, a company linked to the Raelian movement that
believes space aliens created humans by cloning themselves?
“They’re totally out in left field,” Silber says.
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