Fertile couples with repeated miscarriages should be evaluated for the presence of a chromosomal abnormality. The female or male partner may be a carrier of a balanced translocation or may be an aneuploid mosaic. Aneuploidy refers to an abnormal number of chromosomes. An extra or missing chromosome is a common cause of genetic birth defects. Aneuploidy occurs during cell division when the chromosomes do not separate properly between the two cells. Chromosome abnormalities occur in 1 of 160 live births, the most common being extra chromosomes 21, 18 and 13.
Preimplantation genetic testing (PGT) is most frequently recommended for patients who are at risk for genetic disorders such as cystic fibrosis, Tay Sachs disease, or thalassemia. PGT is also helpful for patients with unexplained infertility, a history of recurrent miscarriage, unsuccessful IVF cycles, advanced maternal age, or male factor infertility. In these cases, the most likely cause is a chromosome abnormality.
Chromosome abnormalities include aneuploidy and structural abnormalities. Aneuploidy is the most common chromosomal abnormality and it occurs in both eggs and sperm. Structural abnormalities in both eggs and sperm include translocations, inversions, and deletions. The transmission of a chromosome abnormality to an embryo can result in a low implantation rate, miscarriage, or the birth of a baby with a genetic disorder.
Is there help for recurrent miscarriage?
Dr. Isaac Glatstein, Associate Medical Director at the Reproductive Science Center of New England, is a fertility doctor in Massachusetts. A Board Certified Reproductive Endocrinologist, he provides fertility screening and infertility treatment at the RSC New England fertility clinics in Braintree and Lexington, Massachusetts.
Unsuccessful IVF Cycles
Couples with repeated unsuccessful IVF cycles should be evaluated for the presence of a chromosome abnormality. The female or male partner may be a carrier of a balanced translocation or may be an aneuploid mosaic.
The most probable cause of unexplained infertility or history of habitual miscarriage is a chromosome abnormality. The male or female partner may be a carrier of a translocation or may be an aneuploid mosaic.
Aneuploidy and Advanced Maternal Age
Women 35 and older are at a higher risk of producing aneuploid embryos, which results in implantation failure, a higher risk of miscarriage or the birth of a child with a chromosome abnormality such as Down syndrome.
All of a woman's eggs are present at birth. 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. Studies have shown that approximately 62 percent of embryos from women of advanced maternal age might be aneuploid. 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 if PGT should be considered.
Male Factor Infertility
Approximately one-half of all infertility is caused by sperm abnormalities. Many sperm disorders are due to a chromosome abnormality such as aneuploidy or a structural chromosome abnormality. Men who carry a balanced translocation chromosome are at risk of producing sperm with a structural chromosome abnormality. Studies have shown that approximately 3 to 8 percent of sperm from normal, fertile men are aneuploid and 27 to 74 percent of sperm from men with severe infertility are aneuploid. Couples with infertility due to male factor should consider chromosome analysis of the male’s sperm prior to IVF.
Y Chromosome Deletions and Infertility
Y chromosome deletions are found in approximately 5 to 20 percent of males with a very low sperm count. These deletions appear to impair normal sperm development. While these deletions do not appear to cause any genetic disease, they appear to decrease the chance of men with a low sperm count to successfully fertilize eggs in a normal way.
This information is provided for general education purposes and is not intended to take the place of a discussion with your physician. If you have questions about any aspect of your health, you are advised to speak with your physician.