After a failed round of IVF, many couples are already suffering from more than enough disappointment and willing to do anything that will help raise their chances of successful conception. Preimplantation Genetic Testing, or PGT, has become increasingly popular as many couples turn to this strategy to increase their odds of a successful pregnancy. While this method can increase the odds of a successful transfer and pregnancy, it does not guarantee the results you’re hoping for.
PGT Success Rates
PGT can substantially raise the odds of getting pregnant each cycle. Unlike natural fertility rates, which fall around 10% per cycle, the overall rate of live birth after transferring one embryo after PGT is about 50-60% per cycle–a substantial increase that can build hope for many families.
When PGT was first introduced, scientists–as well as hopeful parents-to-be–were hoping for a success rate of around 70-80%. Unfortunately, that didn’t hold true once PGT became reality, tested outside the laboratory environment. The procedure does, however, greatly increase the odds of a successful pregnancy, making it an ideal choice for many families who want to increase their odds of pregnancy as soon as possible.
Potential Causes of PGT Failure
The uterus has been prepared carefully with the right hormones an ideal setup. The chosen embryo, thanks to PGT, has a greater than 90% likelihood of being normal. Why doesn’t the embryo implant successfully?
Multiple factors contribute to a successful implantation and pregnancy. A variety of factors can, unfortunately, lead to failure in any given IVF cycle, including one with PGT. Consider these possibilities for failure of an IVF cycle with PGT.
1. Undetected embryo abnormalities
Current embryo screening technologies are highly accurate, but there is still around a 2-3% inaccuracy rate when testing for chromosomal abnormalities. The test can still miss some small structural abnormalities in the chromosome which can ultimately lead to an abnormal embryo, which might not implant or grow successfully. PGT also does not routinely search for gene mutations, which could lead to an embryo incompatible with life.
2. Embryo mosaicism
Some embryos have a mixture of normal and abnormal cell lines, and since PGT does not test every cell individually, it could indicate that the embryo is entirely normal when, in reality, the embryo has a group of abnormal cells. Some mosaic embryos do repair themselves, growing into normal embryos that result in live birth. These mixed embryos, however, have a lower chance of becoming live births than normal embryos.
3. Uterine problems
PGT identifies potential problems and complications with the embryo, not with the uterus. Polyps and fibroids in the uterine cavity can destabilize the endometrium or cause local inflammation, which can prevent implantation or lead to problems with the pregnancy. Women who struggle to get pregnant over several cycles may need to have a saline sonogram or hysteroscopy to help identify any potential problems with the uterus before embryo transfer.
4. Endometrial receptivity
No one knows for certain whether or not the uterine lining will be receptive to an embryo, despite extensive testing and preparation. In fact, endometrial receptivity remains one of the biggest mysteries of reproductive science. The hope is that a healthy embryo will be transferred within the implantation window after several days of progesterone supplementation. In a natural cycle, the embryo implants around the 6th or 7th day after ovulation. During an IVF cycle, we try to transfer the embryo between the 6th and 7th day of progesterone exposure to make the cycle as close to nature as possible and increase the chance of implantation.
5. Suboptimal endometrium
If the endometrium is too thick or too thin before starting progesterone, it decreases the odds of a successful IVF cycle. In an ideal cycle, endometrium thickness ranges between 7.5 and 10 mm. Many factors can contribute to a thin endometrium, including:
- Low estrogen
- Low uterine blood flow
- Scarring from a previous surgery or procedure, including D&C or myomectomy
We use several tactics to help improve a thin uterine lining and increase the odds of implantation, including:
- High doses of estrogen
- Vaginal Viagra
- Vitamin E
- Endometrial biopsy or “scratching” to stimulate the endometrium to regenerate more vigorously and become “stickier” in the subsequent cycles.
6. Technical limitations of the laboratory
While we now have the ability to replicate many things in the lab and grow embryos to implantation stage, technical limitations in the laboratory and the embryologists can affect the chance of PGT success.
For safe biopsy, the embryos need to be grown to the blastocyst stage when the cells that make up the embryo (the inner cell mass) can be clearly seen and avoided during the biopsy procedure. The embryologist has to be skilled in performing the biopsy.
Too vigorous a biopsy can remove too many cells and damage the shell of the embryo that can result in lower embryo health upon thawing during future transfer. A timid biopsy, on the other hand, can yield insufficient cells for diagnosis that might require in repeat biopsy. In the right hands, the embryo survival rate is higher than 95%. Careful attention in the laboratory environment is critical to ensuring the success of the testing and increasing transfer success rates.
Many couples have already struggled for years to become pregnant before turning to IVF. After so much emotional, physical, and financial investment, a failed embryo transfer can be very devastating, leaving you feeling discouraged and wondering if you’re ever going to have your baby in your arms.
But don’t despair, after a failed cycle, your physician and care team will have more information to help you achieve a better outcome next time.
With PGT, you can substantially increase your chance of receiving a healthy embryo and raise the odds that you will become pregnant. While it’s not a surefire recipe for success, PGT does considerably raise your chance of having a baby.
Want to learn more? Contact us today to discuss our highly-trained medical professionals, our compassionate care, and our success rates–including the odds that we will be able to make your dreams of increasing the size of your family come true.