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PGD and Frozen Embryo Transfer For Women Over 40
February 11, 2013
The latest buzz in the field of fertility treatment is frozen embryo transfer (FET) for safer and more successful in vitro fertilization (IVF) cycles. Studies have found that by transferring a thawed embryo in a subsequent cycle, the risk of ovarian hyperstimulation syndrome (OHSS) is minimized and the uterine lining has time to recover from the harsh effects of fertility drugs. Preimplantation Genetic Diagnosis (PGD), in particular Comprehensive Chromosome Screening (CCS), performed in conjunction with FET maximizes the fertility patient's chance of successful pregnancy. The benefits of safer and more successful cycles are obvious for all patients, but perhaps the greatest benefit is to women over the age of 40.
Christo Zouves, M.D. of Zouves Fertility Center in Foster City, CA. says new developments in the field have not only increased the success rates for IVF overall, but have also given fertility doctors the ability to eliminate factors that might cause an IVF cycle to fail. “The issues over the years with IVF have been why success rates are low and why pregnancies fail. In the early days of IVF, we transferred many embryos just to achieve a pregnancy. In the last two years, FET rates have increased steadily to the point where they are even better than fresh transfer rates,” he says. Combined with the benefits of genetic testing, fertility doctors are now able to maximize the potential of a fertility treatment cycle moving closer to the goal of IVF: a single embryo transfer with 100% implantation and live birth success.
How Vitrification Increases Success Rates
In the past, slow freeze methods for preserving embryos were not as successful as the vitrification techniques used today. Approximately 60-70% of slow-freeze embryos survived the thaw process, and 30% of did not survive at all. Vitrification results in lower incidence of ice crystal formation and a 98% survival rate post-thaw- a vast improvement from traditional methods.
“It is a no-brainer to do a natural ovulation (without fertility drugs) or controlled (using fertility drugs to prepare the uterine lining) frozen transfer. The embryos are frozen on day 5 or day 6 and are put back at the time an embryo would reach the uterus in nature. Doing a delayed transfer gives the uterine lining time to recover from the effects of the fertility drugs and you may have even genetically tested the embryo to know the likelihood it will develop into a healthy pregnancy,” Zouves states.
Benefits of PGD Over 40
Around 60% of all pregnancy losses are the result of a genetic abnormality in the embryo which inhibits its ability to develop into a healthy pregnancy. Women over the age of 35 are more inclined to suffer pregnancy loss due to genetic abnormality, and women over the age of 40 will only see one normal embryo for every six embryos.
Comprehensive Chromosome Screening (CCS) gives fertility doctors the opportunity to transfer one embryo with greater confidence. CCS compares the biopsied cell of an embryo to a template, much like a score card on a standardized test. The template shows the genetic pattern of a completely normal embryo and highlights any indications of an abnormal reading on all 23 chromosomes with over 99% accuracy.
What this means for women over 40, or those with low ovarian reserve, is that several stimulation cycles can be done in succession to retrieve a higher number of eggs. These eggs undergo intracytoplasmic sperm injection (ICSI) and CCS in one batch and are frozen for the next cycle. These processes yield 30% IVF success rates for women over 40 who might see success rates less than half of that without vitrification and genetic testing.
“We are almost at the holy grail of IVF, much closer than we were even one year ago,” Zouves says. He especially advises patients who have suffered multiple failed cycles to consider genetic testing. CCS will not only save a fertility patient from undergoing several failed cycles to get one normal pregnancy, but would also help them to move to donor egg IVF where indicated.