Embryos created from In Vitro Fertilization (IVF) cycles can be genetically tested before being returned to a woman’s uterus for implantation. Preimplantation Genetic Testing (PGT) refers to innovative technologies to biopsy the part of an embryo (trophectoderm) which later becomes the placenta.

Reasons for Testing

Genetic testing allows for selection of genetically normal embryos that may decrease the risk of miscarriage and improve the overall safety and efficiency of an IVF cycle. We know that genetically abnormal embryos are more common in patients as they get older. Genetic testing aids in the selection of a single healthy embryo for transfer and decreases the risk of multiple birth. In addition, genetic testing can be used to select embryos free from specific genetic diseases, such as Cystic Fibrosis. Both single gene mutations (PGTm) and the entire DNA complement (PGTa) can be analyzed after embryo trophectoderm biopsy.

There are a number of reasons you may want to consider genetic testing. Your physician will work with you to determine if it is right for you.

Indications for PGT

Genetic testing is often recommended for patients with unexplained infertility, recurrent miscarriages, unsuccessful IVF cycles, advanced maternal age, and male factor infertility. The most likely cause in these cases is a chromosome abnormality. Chromosome abnormalities include aneuploidy and structural abnormalities, with aneuploidy being the most common—it can occur in both eggs and sperm.

Structural abnormalities include translocations, inversions, and deletions. These abnormalities can be present in both eggs and sperm. The transmission of a chromosomal abnormality to an embryo can result in low implantation rates, miscarriage, or the birth of a baby with a genetic disorder. Using Preimplantation Genetic Testing (PGT), the scientists in our Embryology Laboratory can identify the absence of these specific genetic disorders in each developing embryo. As a result, only those embryos free of the structural abnormality will be transferred to the patient’s uterus, with the goal of increasing the chance of conception and ultimately the birth of a healthy baby.

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There are many reasons why some women choose not to have children - but perhaps the most heart-breaking reason is to prevent passing an inherited genetic disease to your child. However, because of advancements in reproductive medicine available right here in the northwest, parents facing those problems are getting peace of mind and having healthy babies.

Aneuploidy and Advanced Maternal Age

Women of advanced maternal age (over 35) are at a higher risk of producing aneuploid embryos. A woman is born with all the eggs she will ever have. Over time, the chromosomes within the egg are less likely to divide properly, resulting in cells with too many or too few chromosomes. Aneuploidy is also believed to be a major reason for the decrease of fertility with age. Prior to attempting a pregnancy, women in this age group may wish to talk with their physician or a medical geneticist about their chances of having a child with a genetic disease and how PGT may be able to help.

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Maternal Age Trisomy 21Trisomy 18Trisomy 13
15 - 191:1250 1:17000 1:33000
20 - 241:1400 1:14000 1:25000
25 - 291:1100 1:11000 1:20000
30 - 341:700 1:7100 1:14000
35 - 391:200 1:2400 1:4800
40 - 441:60 1:700 1:1600
Maternal Age Trisomy 21 Trisomy 18 Trisomy 13
15 - 191:1250 1:17000 1:33000
20 - 241:1400 1:14000 1:25000
25 - 291:1100 1:11000 1:20000
30 - 341:700 1:7100 1:14000
35 - 391:200 1:2400 1:4800
40 - 441:60 1:700 1:1600

Male Factor Infertility

Approximately half of all infertility is caused by sperm abnormalities, with the majority of cases due to a chromosome abnormality such as aneuploidy or structural chromosome abnormality. Men carrying a balanced translocation chromosome are at risk of producing sperm with a structural chromosome abnormality. Research has shown that approximately 3% to 8% of sperm from normal, fertile men are aneuploid. In contrast, between 27% and 74% of sperm from men with severe infertility (i.e. low sperm count, low motility, poor morphology) are aneuploid.

Y chromosome deletions are found in approximately 5% to 20% of males with a very low sperm count. These deletions appear to impair normal sperm development. While these deletions do not necessarily cause any genetic disease, it appears to decrease the chance of men with a low sperm count to successfully fertilize eggs. Couples with infertility due to male factor should consider chromosome analysis on the male reproductive partner’s sperm prior to IVF.