New York, NY (PressExposure) July 12, 2011 -- A leading IVF center in NY has announced research suggesting that genetic control over the mother's immunologic tolerance of embryos is behind some IVF failures. According to the Center for Human Reproduction, genetics can have an effect on the implantation of embryos. After over four million IVF babies worldwide and a Nobel Prize in Medicine and Physiology to recognize the accomplishment, the reality of IVF is that more IVF cycles still fail than succeed.
A majority of failed IVF cases (and miscarriages) are considered to be a result of chromosomal abnormalities in embryos. In a smaller number of cases-estimated by some authorities to represent approximately 15% of failed IVF cycles-implantation fails because the process of implantation itself malfunctions. "Implantation is an immunologic process," explains Norbert Gleicher, MD, Medical Director at the IVF NY center CHR and an international expert in the immunology of reproduction. "Because the genetic material of the implanting embryo is half paternal, for the mother's immune system, the embryo is analogous to an organ transplant. Under normal circumstances, however, this 'transplant' is not rejected."
Why the maternal immune system tolerates this "transplant" is also not well understood. However, recent research at CHR suggests a genetic component. Investigators at CHR recently closely linked a gene on the X-chromosome, the so-called FMR1 gene, with ovarian aging and chances of conceiving with IVF: women with so-called normal genotype had almost double the pregnancy chance with IVF as women with so-called heterozygous-normal/low genotype.1
A follow-up study, also in the medical journal PLoS ONE, suggested that FMR1 differences are also likely responsible for variations in IVF pregnancy rates in different races/ethnicities.2
David H. Barad, MD, the Center's Clinical Director of IVF explains: "We now have evidence that IVF outcome differences associated with FMR1 affect implantation. They are likely immunologic in nature." These are the first reported genetic controls for IVF outcomes. "This genetic component to embryo implantation may lead to prognostications, based on IVF patients' genetic profiles," adds Dr. Gleicher. "Potentially, then, these prognostications may open up revolutionary new avenues to therapies to improve implantation and IVF pregnancy chances through immunologic treatments."
1Gleicher et al., PLoS ONE 2010; 5(12): e15303; 2Gleicher et al., PLoS ONE 2011; 6(4): e18781