Recently, I saw a new patient who wanted to be evaluated for difficulty in becoming pregnant. She told me that a close friend of hers had recently delivered a baby with a genetic disorder. The patient seeking our assistance was very worried about having a similar experience.
It turns out that the patient’s friends (both the man and the woman) were carriers of a recessive gene that combined during fertilization. The combination of these two recessive genes resulted in the child developing the disease. Diseases that result from the combination of a recessive gene from each parent is referred to as an autosomal recessive disorder. Although neither the mother nor the father of the child had an abnormality, both were carriers of the recessive gene. In this situation, the baby from this couple had a 25% chance of developing the disease. If the child did not develop the disease, then the child had a 50% chance of being a carrier and a 25% chance of not being affected at all.
It is estimated that every person may be a carrier of several recessive genes. If there has not been a child born in her family with an abnormality, the couple may have no knowledge of being a carrier of a recessive gene. Unfortunately, this may not be discovered until he couple has a child with a genetic disorder. It is preferable to test the man and the woman prior to conception to determine if they are carriers and avoid a genetic disorder, rather than test them after an affected child has been conceived.
Today, there is available testing for the man and the woman for a DNA analysis with the ability to indentify over 100 recessive genes. Some of these have been recommended by the American College of Obstetricians and Gynecologists at their visit for preconception counseling. If it is discovered that the man and woman are carriers for the same disease, the couple can elect to undergo a cycle of in vitro fertilization (IVF) with pre-implantation genetic screening (PGS) and transfer unaffected embryos to avoid having a child with the genetic abnormality. Although a couple could elect to undergo insemination with donor sperm or to undergo a donor oocyte cycle, IVF with PGS is usually more desirable. All of these procedures allow the couple to avoid having a child with the genetic disorder that could have resulted from the combination of their recessive genes.
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