Genetic abnormalities are one of the more common causes for miscarriage and can contribute to infertility. The expression "It's nature's way..." is often accurate; the body has rejected the pregnancy because it was not quite right. However, we want to know more than why the pregnancy was rejected; we want to know why it was abnormal in the first place. The test known as a karyotype involves analysing you and your partner's chromosomes for abnormalities. Tests can be performed to determine whether:
- Either of the parents has a chromosome rearrangement that will give a higher chance of genetic imbalance in the eggs or sperm (blood karyotyping). This test is commonly used for couples who have had repeated miscarriages or several failed IVF cycles.
- The embryo has a chromosomal disorder e.g. Down syndrome (preimplantation genetic diagnosis). This test can be performed with an IVF cycle to ensure that only embryos without an error for the chromosomes tested are transferred.
- The fetus has a genetic disorder (prenatal testing) such as cystic fibrosis or Down syndrome.
Chromosomes
Normally there are 46 chromosomes in humans. These chromosomes carry all of the different genetic messages that determine our appearance and function. Any problem in them can cause serious diseases and abnormalities. It is now possible to test for the presence of abnormalities of both chromosome number and structure. This may allow infertility specialists to diagnose the cause of some problems. Specific genes which if altered or missing can cause diseases which affect fertility can be tested for: Cystic Fibrosis and Haemochromatosis are examples.
Cystic Fibrosis
This is a potentially serious condition which can commonly cause premature death due to chronic lung infections and diabetes. It is due to altered genes which affect the ability of cells to transport fluid into and out of them. Somehow this condition affects the way in which the vas deferens (sperm transport tube) develops. The genes that cause cystic fibrosis can be abnormal but still not cause such serious disease. It is possible for men to have congenital absence of the vas deferens alone without cystic fibrosis. This situation occurs in 1% of infertile men.
Haemochromatosis
This condition leads to the accumulation of too much iron in the body. It can cause liver disease, tiredness and joint aches and pains. It can affect fertility by depositing excess iron in various glands such as the pituitary, testes and ovaries. A simple test of iron stores can determine the risk of carrying the disease. Treatment is usually as simple as donating blood on a regular basis.
A range of other genetic abnormalities are associated with infertility and miscarriage. Your doctor can advise you of what testing is recommended at the time of your consultation.
Pre-implantation Genetic Diagnosis
It is possible to undertake almost any genetic test that can be performed on an adult human on just a single cell of an embryo. This requires the use of In Vitro Fertilisation (IVF) with Pre-implantation Genetic Diagnosis (PGD).