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 babies with 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.
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.
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.
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.