Any abnormality in an individual genetic makeup may cause a Genetic disorder. It can range from minor to major depending upon simple mutation in a DNA strand of single gene to gross abnormality of whole chromosome or set of chromosomes.
Some genetic disorders are inherited from parents, it runs in the family from generation to generation or it can be acquired randomly because of mutation or changes in a single gene or group of genes. It can be due to environmental factors, toxins, exposure to certain chemicals, radiations etc.
Factors increasing the risk of genetic disorders are :
- Age – incidence increases steeply after 35 years of age.
- Family history
- Previous history of miscarriages and birth defects.
- Cancer history, have undergone chemo/radiotherapy.
Pre genetic counseling is important for this group of patients before planning for pregnancy or undergoing treatment.
They should undergo pre genetic tests to assess the risk of transmitting the disease to the child.
If the risk is high then there are other options to look for :
- IVF with its own gametes along with pre-genetic testing of formed embryos to rule out the diseased embryos and to transfer genetically healthy embryos to give a healthy baby.
- Artificial insemination with donor sperm
- Donor egg IVF – taking healthy eggs from a young fertile lady.
Genetic disorders because of chromosome abnormalities may be due to an abnormal number of chromosomes or due to structural defects in chromosomes. Most of the miscarriages before 9weeks are due to genetic abnormalities. Down syndrome is the most common chromosomal disorder in live-born babies.
Some common genetic disorders are :
- Down syndrome is the most common genetic disorder where extra genetic material from chromosomes is transferred to newly formed embryos. Instead of 46 chromosomes, the foetus has 47 chromosomes (3 chromosomes 21). Most commonly seen due to the advanced age of the female partner. Incidence increases above 35 years of age. The mutation in the genes causes physical and mental abnormalities in the developing foetus.
- Thalassemia Disorder is an inherited genetic blood disorder that causes the body to form less haemoglobin than normal. It can be minor or major. Mild forms may not need treatment while major forms require a frequent blood transfusion. Passing on Thalassemia to the offspring can be prevented to an extent by getting both partners screened for the disease before planning for pregnancy.
- Sickle cell disease is also an inherited disorder of haemoglobin in the blood, commonly affecting Africans. Sickle cell anaemia is because of abnormal sickle-shaped red blood cells blocking the flow of blood.
- Muscular Dystrophy is a muscle disorder, runs in families. It is because of faulty genes inherited by one or both parents. There is a mutation of the gene responsible for healthy muscle structure and function.
- Cystic fibrosis is an inherited disorder characterized by the buildup of thick, sticky mucus damaging the respiratory and digestive systems.
- Congenital adrenal hyperplasia is an inherited disorder having a low level of cortisol and high level of male hormones resulting in the development of male features in females and early onset of puberty in both boys and girls.
- Consult your doctor prior to planning pregnancy if any of the diseases run in the family to have a healthy baby.
(Authored by Dr Ila Gupta, Senior consultant IVF & Clinical Director, Ferticity Fertility Clinics, Delhi)