Chromosomal abnormalities are common in embryos, and are one of the main reason women fail to conceive with IVF (or spontaneously) as they age. It is known that about 60% of embryos in women under 35 years of age and 80% of embryos in women over the age of 41 will be chromosomally abnormal.
Preimplantation genetic diagnosis is used to identify genetic defects in embryos created through assisted reproduction (IVF) prior to the embryos being implanted in a woman’s uterus, and hopefully increasing the likelihood of a normal pregnancy. In general, there are 2 types of preimplantation genetic testing, Preimplantation Genetic Diagnosis (PGD) and Preimplantation Genetic Screening (PGS).
PREIMPLANTATION GENETIC DIAGNOSIS (PGD)
Preimplantation Genetic Diagnosis (PGD) specifically refers to the genetic testing that occurs on an embryo from parents known to carry a genetic abnormality. The embryos created for the couple are tested to see if the embryo(s) carries the same genetic defect as the parent(s). PGD testing can occur for genetic diseases (referred to as testing for single gene defects) or for chromosomal abnormalities.
PREIMPLANTATION GENETIC SCREENING (PGS)
In contrast, Preimplantation Genetic Screening (PGS) or Complete Chromosomal Screening (CCS) refers to the chromosome testing performed on an embryo from genetically normal parents, who have a higher likelihood of having a baby with a chromosomal abnormality. The embryos intended for CCS are screened to see if they carry a chromosomal defect only (such as Trisomy 21 or Down’s Syndrome). Screening for genetic diseases (such as Cystic Fibrosis or Sickle Cell Anemia) does not occur with CCS.
BENEFITS OF PGD & PGS
In both PGD and PGS, because only embryos that do not carry the genetic defect are transferred back into a woman’s uterus, these techniques decrease the incidence of children born with chromosomal abnormalities, children born with genetic diseases, or miscarriages in the parents using IVF with preimplantation genetic testing to conceive.
Sometimes, the couples in need of these techniques are NOT infertile. In fact, in most cases of PGD for genetic diseases, the couple has had an affected child and is seeking the opportunity to decrease the risk of having another child with significant health compromise and/or early death.
PGD/PGS is used for patients/couples in which:
- The female partner is 35 years of age or older and at increased risk for having a child with a chromosomal abnormality (PGS)
- The couple has had recurrent miscarriages of unknown cause (PGS)
- The couple has had a previous child or pregnancy with a chromosome abnormality (PGD)
- The couple is concerned about having a child with a chromosome abnormality (PGS)
- The couple has had a previous unsuccessful IVF cycle despite good quality embryos (PGS)
- One member of the couple carries a known chromosomal defect (PGD)
- The couple is at risk of having a child with an inherited single gene genetic disease (PGD)
Preimplantation genetic testing utilizes in vitro fertilization where multiple eggs are matured and retrieved. The oocytes are then inseminated with a single sperm (ICSI), and grown in culture until biopsy. The most common approach for PGD/PGS is to biopsy embryos on Day 5, 6 or 7, at the expanded blastocyst stage.
This procedure is called trophectoderm biopsy. Many more cells are removed for analysis with this technique, compared to the older technique of testing embryos on day 3 of growth. With the new freezing technique of vitrification, the embryos are typically frozen and transferred at a later date, and it is associated with high success.
GENETIC TESTING TECHNIQUES
There are several techniques for assessing the chromosomal complement of embryos. The older technique utilized was FISH (Flourescent In Situ Hybridization), in which only 9 chromosomes out of 24 were tested. Initial reports showed that the FISH technique did not seem to improve pregnancy rates in women using the technique to screen for chromosomal abnormalities. The lack of improvement in the pregnancy rate seen with the FISH technique was felt to be due to the fact that less than half of the chromosomes were actually tested.
Newer methods were then developed to overcome this problem. There are only 2 techniques utilized for IVF patients that produce a comprehensive chromosomal analysis and analyze all 24 chromosomes of a single cell. These techniques are microarray CGH (comparative genomic hybridization) and SNP microarrays (single nucleotide polymorphism). Essentially, both techniques use florescent dyes to test the genetic makeup of the cell. The results typically take several hours.
(Does not include the costs for medications, genetic screening, medications for the cycle and post embryo transfer/ retrieval treatment)
- One IVF cycle with ICSI and 24 chromosome aneuploidy diagnosis with day 5 biopsy and subsequent Frozen embryo transfer of normal embryos- $14,900 (cash price)
- One IVF cycle with testing for a single gene defect- $14,900*. This price does not include the genetic testing as this price is variable based on the disease being tested and work up needed prior to biopsy.
*These prices do not includes the genetic testing performed by an outside genetic lab. Please set up a consult to discuss which of the above options is best for you.