Genetic Testing Improves PFC Success Rates
Along with improved freezing technology and biopsy methods, much of this success at PFC and elsewhere is due to advances in chromosomal screening, said Lauri Black, a certified genetic counselor at PFC.
Advances in genetic testing
Weve offered chromosome screening for well over a decade, she said, but PFC became an enthusiastic early adopter of comprehensive chromosome screening (CCS) due to its greater accuracy and effectiveness over previous methods. We now offer CCS to the majority of our patients.
CCS uses a DNA-based method called a microarray to see whether or not there is an imbalance in the amount of chromosomal material. It checks for extra or missing chromosomes, testing all 23 pairs of chromosomes, said Black, which wasnt possible with previous genetic testing methods.
What CCS can and cannot test for
CCS is a sensitive and specific test for chromosomal aneuploidy, the presence of abnormal numbers of chromosomes in the embryo. Abnormal numbers of chromosomes are very common in early embryos; CCS identifies embryos that have normal numbers of chromosomes, known as euploid embryos.
Patients often misunderstand what CCS can and cannot do, said Black, who has been active in the field for 17 years and who calls genetic counseling a burgeoning field involving both science and psychosocial impacts on patients. Subspecialty areas within genetics include assisted reproduction technologies, infertility genetics, and prenatal diagnosis.
I clearly explain that CCS tests specifically for chromosomal abnormalities such as Down syndrome, which can randomly happen with individual embryos and is more common in older women, she said. It cant screen for birth defects unrelated to a chromosomal abnormality, such as a heart defect or cleft lip, as well as autism, many learning disabilities, and adult-onset conditions that run in families, such as heart disease, diabetes, and psychiatric conditions.
CCS also doesnt test for specific single-gene genetic diseases known to run in families such as cystic fibrosis, Huntingtons disease, or a breast cancer gene mutation. These can be screened with preimplantation genetic diagnosis (PGD), which is less frequently performed than CCS, said Black, because genetic diseases are much less common than chromosomal abnormalities.
Using CCS to select and transfer only embryos with normal chromosomes, PFC has seen significant reductions in the rates of miscarriage and consistently better implantation rates and ongoing pregnancy rates, eventually leading to the birth of a baby. Its a powerful tool in determining which embryos might lead to a successful pregnancy, said Black.
In fact, by identifying and transferring a single euploid embryo after in vitro fertilization (IVF), Pacific Fertility Center has been able to improve per transfer pregnancy rates to 5075 percent per transfer in all age groups, reduce multiple gestation rates to under 2 percent per transfer, and substantially reduce the risk of miscarriage and clinical aneuploidy, such as Down syndrome.
In young women, CCS improves per transfer pregnancy rates, reduces the risk of multiple gestation, and enables fertility preservation of embryos, saving euploid embryos for later use. In older age groups that have fewer euploid embryos, the benefit of chromosomal screening is even stronger. The greatest improvements have occurred in women ages 35 to 42, she said. These are women who are at greater risk for chromosomal abnormalities, but who generally have enough follicles and can create enough embryos, so its still possible to find normal embryos to transfer.
Some patients, especially older women, may need to do multiple cycles to find a chromosomally normal embryo, said Black. Due to the greater risk of miscarriage and reproductive failure, PFC will not transfer any embryos that are not euploid. We educate patients about this before performing CCS, making it clear that any type of genetic testing is entirely optional for all patients.