Genetic screening before IVF significantly reduced the rate of pregnancies in women between 35-41 years of age.
FERTILIZATION IN VITRO
There were 350,000 IVF cycles in 2002, with half of the women over 35 years of age. They tend to have more chromosomal abnormalities in their embryos.
Genetic screening before implantation involves aspirating a single blastomere from each embryo, and identifying the copy numbers of a set of chromosomes. It was to become the standard procedure before IVF.
Indeed, there is a higher implantation rate for transferred embryos, but no increase in the rated of successful pregnancies. Instead, it significantly reduced the live birth rates after IVF.
The pregnancy rate per aspirated follicles is 11.7% in the group having genetic screening before implantation and 14.7% in the control.
The number of chromosome analyzed with FISH leads to transfer labeled embryos normal that are in fact abnormal and anacuploid.
Many human embryos are mosaic so their chromosomal constitution may not represent the entire embryo.
SOURCE: NEJM 7.5.07
MEDICAL COMMENTARY
The primary outcome in fertility studies should be live births since that is the goal of the treatment. Biopsy of a blastomere on day 3 has the potential of an embryo to successfully implant and increases the chance of a live birth by 80%.
These results oppose routinely performing genetic screening before implantation as an aid to IVF.
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