What is preimplantation genetic diagnosis?
Preimplantation genetic diagnosis refers to the testing of embryos for genetic disorders prior to their implantation in the uterus. This technology is very similar to prenatal genetic testing but offers the advantage of getting the results prior to a pregnancy being established. When the embryo is tested for all 24 chromosomes the technology is referred to as preimplantation genetic screening, and when the embryo is tested for a specific genetic defect, such as cystic fibrosis, it is called preimplantation genetic diagnosis.
Preimplantation genetic diagnosis is similar to prenatal genetic testing, but offers the advantage of getting the results prior to a pregnancy being established.
How does PGD work?
In order to test embryos, a couple must go through an in vitro fertilization (IVF) cycle where oocytes, or eggs, are extracted from the ovaries. Fertilization of the oocytes occurs in the laboratory and the resulting embryos are grown in culture (typically for five to six days) until they develop into blastocysts. Blastocysts are embryos that have differentiated into an inner cell mass (the part that becomes the baby) and the trophectoderm (the part that becomes the placenta). A small biopsy from the trophectoderm is conducted and these cells, typically five to 10 in number, are tested for genetic problems. Most commonly, the tested embryos are then frozen to later be used if the results are normal. Alternatively, the normal or unaffected embryo(s) may be transferred into the uterus the following day.
Who is a candidate for PGD?
Preimplantation genetic screening is primarily utilized in women who may be at increased risk of having a child with a chromosomal problem. This includes women who are of advanced reproductive age (35 years of age or older), have low ovarian reserve, have a history of having a child affected by a chromosomal abnormality, or have a history of recurrent miscarriage. Preimplantation genetic diagnosis is a great option for couples at increased risk of having a child with a specific genetic disease including sickle cell disease, cystic fibrosis, Beta-thalassemia, Hunington’s disease, and Duchenne muscular dystrophy to name a few.
Mika R. Thomas, M.D., is a board-certified reproductive endocrinologist and infertility specialist. She obtained her bachelor of science degree in the biological sciences from Southern Methodist University. Dr. Thomas went on to attend medical school at the University of Texas at San Antonio. Dr. Thomas was elected a member of the prestigious Alpha Omega Alpha Honor Medical Society while in medical school. Dr. Thomas completed her internship and residency in obstetrics and gynecology at Maricopa Medical Center and St. Joseph’s Hospital where she conducted and presented research on topics including the predictors of embryo transfer success rates, IUI preparations, and the medical management of miscarriages. Dr. Thomas finished a fellowship in reproductive endocrinology and infertility at the University of Iowa Hospitals and Clinics. During her fellowship, she received specialized training in the diagnosis and treatment of various causes of infertility including polycystic ovarian syndrome, diminished ovarian reserve, tubal factor, and male factor. During her fellowship, she performed assisted reproductive technology (IVF) cycles as well as trained in fertility microsurgery. Dr. Thomas is a member of the American College of Obstetricians and Gynecologists, the American Society for Reproductive Medicine, the Society for Reproductive Endocrinology and Infertility, the American Medical Association, the American Association of Gynecologic Laparoscopists, the Alpha Omega Alpha Honor Medical Society, the Texas Medical Association, the Dallas County Medical Society, and the Dallas Area Reproductive Endocrinologists.