Infertility and genetics

SIGNIFICANCE: Infertility is a disease of the reproductive system that impairs the conception of children. About one in six couples in the United States is infertile. The risk that a couple’s infertility may be caused by genetic problems such as abnormal sex chromosomes is approximately one in ten.

A Reproductive Disease

Infertility is a disease of the reproductive system that impairs a couple’s ability to have children. Sometimes infertility has a genetic cause. The conception of children is a complex process that depends upon many factors, including the production of healthy sperm by the man and healthy eggs by the woman, unblocked Fallopian tubes that allow the sperm to reach the egg, the sperm’s ability to fertilize the egg when they meet, the ability of the fertilized egg (embryo) to become implanted in the woman’s uterus, and sufficient embryo quality. If the pregnancy is to continue to full term, the embryo must be healthy, and the woman’s hormonal environment must be adequate for its development. Infertility can result when one of these factors is impaired. Physicians define infertility as the inability to conceive a child after one year of trying.

Genetic Causes of Infertility

The most common male infertility factors include conditions in which few or no sperm cells are produced. Sometimes sperm cells are malformed or die before they can reach the egg. A genetic disease such as a abnormality can also cause infertility in men. A genetic disorder may be caused by an incorrect number of chromosomes (having more or fewer than the normal forty-six chromosomes). Having a wrong arrangement of the chromosomes may also cause infertility. This situation occurs when part of the genetic material is lost or damaged. One such genetic disease is Klinefelter syndrome, which is caused by an extra X chromosome in males. The loss of a tiny piece of the male sex chromosome (the Y chromosome) may cause the most severe form of male infertility: the complete inability to produce sperm. This form of infertility can arise from a deletion in one or more genes in the Y chromosome. Fertility problems can pass from father to son, especially in cases in which physicians use a single sperm from an infertile man to inseminate a woman’s egg.

Female infertility may be caused by an irregular menstrual cycle, blocked Fallopian tubes, or birth defects in the reproductive system. One genetic cause of infertility in females is Turner syndrome. Most females with Turner syndrome lack all or part of one of their X chromosomes. The disorder may result from an error that occurs during division of the parent’s sex cells. Infertility and short stature are associated with Turner syndrome. Other genetic disorders in females include X, tetrasomy X, and pentasomy. These syndromes are the female counterparts of Klinefelter syndrome and can be associated with intellectual disability.

About 50 to 60 percent of infertility was estimated to be caused by chromosomal abnormalities. Most babies with these abnormalities would not survive even if they were born. Chromosomal problems are more common if the mother is older and has a history of requiring longer than a year to conceive. Men who are older or who have a history of being subfertile can also contribute to genetic abnormalities. After the age of thirty-five, the structure within a woman’s eggs is more likely to become damaged. Men over the age of forty-five have an increased risk of damage to the structure of the chromosomes in their sperm.

Scientists believe that as their understanding of the genetic basis of infertility problems increases, new therapies will be developed to treat them. Most infertility cases are treated with drugs or surgery to repair the reproductive organs. No treatment is available to correct sex chromosomal abnormalities such as Turner syndrome. However, some women with can have children. For women who cannot conceive, possible procedures include (fertilizing a woman’s egg with sperm outside the body) and embryo transfer (moving the fertilized egg into a woman’s uterus). Adoption is another option for infertile men and women.

Key terms

• in vitro fertilization (IVF)a process in which harvested eggs and sperm are brought together artificially to form a zygote
• sex chromosomesthe chromosomes that determine the sex of an individual; females have two X chromosomes, while males have one X and one Y chromosome

Bibliography

Bentley, Gillian R., and C. G. Nicholas Mascie-Taylor. Infertility in the Modern World: Present and Future Prospects. New York: Cambridge University Press, 2000.

Gordon, John D., and Michael DiMattina. One Hundred Questions and Answers About Infertility. Sudbury, Mass.: Jones and Bartlett, 2008.

"Is Infertility Genetic?" Genome Medical, 2024, www.genomemedical.com/genetic-testing-pregnancy/is-infertility-genetic/. Accessed 5 Sept. 2024.

Jansen, Robert, and D. Mortimer, eds. Towards Reproductive Certainty: Fertility and Genetics Beyond 1999. Boca Raton, Fla.: CRC Press, 1999.

Lewis, Ricki. Human Genetics: Concepts and Applications. 9th ed. Dubuque, Iowa: McGraw-Hill, 2009.

McElreavey, Ken, ed. The Genetic Basis of Male Infertility. New York: Springer, 2000.

Marrs, Richard, et al. Dr. Richard Marrs’ Fertility Book. New York: Dell, 1997.

Potter, Daniel A., and Jennifer S. Hanin. What to Do When You Can’t Get Pregnant: The Complete Guide to All the Technologies for Couples Facing Fertility Problems. New York: Marlowe, 2005.

Rosenthal, M. Sara. The Fertility Sourcebook: Everything You Need to Know. 2d ed. Los Angeles: Lowell House, 1998.

Turkington, Carol, and Michael M. Alper. Understanding Fertility and Infertility: The Sourcebook for Reproductive Problems, Treatments, and Issues. New York: Checkmark Books, 2003.