PGD does not cause birth defects or development problems
PGD Background
For the last 10 years, the techniques of
preimplantation genetic diagnosis (PGD) and preimplantation genetic screening
(PGS) have been used to detect genetic mutations and chromosomal abnormalities
in developing embryos. It has been a revolutionary method that has resulted in
reductions in the rate of miscarriage and babieswith chromosome abnormalities
and has accurately identified hundreds of different genetic disorders in the
embryos of IVF patients.
As women age, the probability for chromosomal
abnormalities increases. PGS involves removing a cell or two from the early
stages of a growing embryo and analyzing the number of chromosomes. Normal human
embryos contain 23 pairs of chromosomes. Commonly however, embryos will contain
too many or too few chromosomes. These abnormalities which are known as
aneuploidies, can lead to implantation failure, miscarriage or birth defects
such as Down's syndrome.
PGD involves removing cells from the early embryo to
test for genetic mutations which can cause disease.
Until lately, only speculation was available about
the effects of preimplantation testing on the child itself. A recent study
presented at the European Society for Human Reproduction and Embryology found
that babies born after PGD/PGS testing had no increased risk of congenital
malformation and no adverse effect on growth.
The test studied three groups of children. 70
singleton babies born after PGD/PGS were compared to an equal number of babies
born through in vitro fertilization and an equal number born through spontaneous
pregnancy.
PGD Study Results
The observations showed no differences in weight,
height, and head circumference at birth or at age 2 in any of the three groups.
While PGD births were more frequently cesarean sections rather than vaginal
deliveries, compared to in vitro fertilization births, they had no more birth
defects, hospital admissions, or surgical interventions than either of the other
two groups.
It is interesting to note that PGD babies at age 2
were healthier than the children from spontaneous conceptions. Researchers
speculate this is due to the fact that women with children conceived naturally
work more than women who conceived children tested with PGD. Mothers who
spontaneously conceived work around 83% of the time compared to mothers with PGD
children working 63% of the time. More time working means more time in day care
for the children, which generally means a less healthy diet.
Complications in pregnancy
There were more complications in pregnancy noted for
the PGD/PGS and in vitro fertilization patients. However, this was expected in
mothers who undergo assisted reproductive therapy. Older women are more likely
to need reproductive therapy compared to younger women. Mothers and fathers of
spontaneously conceived babies were much younger compared to the other two
groups. Lower parental age contributes to fewer complications in pregnancy.
Birth defects
While continuing their study, researchers have not
come up with any significant differences in major birth defect rates. Two PGD/PGS
children, one in vitro fertilization child, and two spontaneously conceived
children were born with major birth defects. Minor birth defects were discovered
in 24 PGD/PGS babies, 23 in vitro fertilization babies, and 13 spontaneously
conceived children. When analyzed statistically, these numbers indicate no
difference in the risk for birth defects in any of the three groups. For more
conclusive data, larger studies would have to be done.
Conclusion
With all of the advances in fetal medicine, embryo
biopsy and PGS are proven to be a safe and accurate technique to diagnose fetal
abnormalities. They could greatly reduce the risk of miscarriage and allow
couples a greater chance for a successful pregnancy without adversely affecting
the health of the child.
Written by Randy Morris
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