Most couples expect a normal baby. However, around 1 in 50 (2%) of babies will have a birth defect. The causes may be genetic (inherited or a sporadic new change in a gene), chromosomal, due to exposure to environmental factors such as viral infections, drugs or a medical condition affecting the mother. Sometimes no cause is apparent.
Genetic conditions are the result of changes in the genes, which are the building blocks of life, unique to each individual. Some parents have conditions that can be passed on to children. These are inherited genetic conditions.
The diagnosis of a genetic condition may be made during pregnancy, after birth, in childhood or later in life.
Genetic conditions are responsible for up to half the admissions to children’s hospitals and around 10% of adult hospitals. There are thousands of genetic conditions, but most are very rare. In the absence of a family history of a genetic condition, there Is not usually a high risk for any specific genetic condition in pregnancy.
Every couple has the population risk (2%) of having a child with a birth defect.
The risk of some conditions in a baby is higher in certain couples due to age, their genes, family history, medication or medical problems in the parents.
Birth defects will vary in severity and may include both intellectual and physical disability.
Genetic counselling enables the couple to consult a genetic counsellor who can discuss the family history, provide the couple with accurate information and help to establish an appropriate estimate of genetic risk. Counselling can also discuss the pros and cons of available testing.
How genetic counselling helps
The main aims of genetic counselling include:
- Help the couple understand a particular genetic condition
- Explain how such conditions are diagnosed
- Determine the recurrence risk of a particular condition
- Discuss strategies on how a family may cope with the risk of a genetic condition during pregnancy
- How to deal with the issues associated with a genetic condition after birth, should it be present in the baby
Although the counsellor can never guarantee the birth of a healthy baby couples often feel reassured about their assessed level of risk following genetic counselling and are likely to feel more confident in their decision-making about screening and testing options.
A detailed family history may reveal who is at risk and who is not.
Current information, both verbal and written, is provided to help people deal with the issues that may arise from the diagnosis of a particular condition.
Decisions regarding family planning are always left up to the parents, and therefore we recommend wherever possible that both parents attend for counselling.
Types of genetic conditions that can be diagnosed
Accurate diagnosis of many inherited conditions is now possible through special laboratory testing.
Chromosomal abnormalities occur when there is a change in the number or structure of the chromosomes. (Normally, we have 46 chromosomes — 22 pairs numbered 1-22 and a pair of sex chromosomes. Boys have XY and girls have XX.) The most common chromosomal abnormality is Down syndrome. There is where there are 47 chromosomes instead of 46, with the extra one being a number 21 chromosome. This is why Down syndrome is also known as “trisomy 21” (strictly translated as three number 21 “bodies,” which can be seen through a microscope.
Image: normal male chromosomes
Image: Down syndrome male
Who should consider genetic counselling
- Pregnant women over the age of 35
- Couples with a concerning family history of a genetic condition such as haemophilia, muscular dystrophy, cystic fibrosis, fragile X syndrome, metabolic conditions, growth disorders, albinism
- Couples who have had a previous baby with a chromosomal abnormality such as Down syndrome
- Women who have had multiple miscarriages, infertility, still births or early infant deaths
- Couples with a child who has a history of hearing or visual impairments, intellectual disability, slow development or seizures
- Couples who already have a child with a serious condition or who have terminated a pregnancy for fetal anomaly
- Consanguineous couples (partners who are close blood relatives) who are planning a family
- Women who are exposed to drugs, radiation or chemical and environmental agents that may cause a birth defect
- Women with a serious medical condition, such as type 1 diabetes or epilepsy
- Couples with a family history of birth defects such as spina bifida, cleft lip and palate, clubfoot, congenital heart disease, etc.
- Couples with a strong family history of cancer
What to expect at a genetic counselling consultation
The genetic counselling consultation will involve taking a detailed family history and the development of a family pedigree or family tree. The counsellor will document the medical details of family members affected by various significant health conditions so the pattern of inheritance can be reviewed. Certain medical tests may be offered, if available, for clarification of risk and the counsellor will explain their advantages and limitations.
Once a definite problem is identified and the diagnosis has been confirmed, the counsellor can estimate the risk involved and discuss the genetic aspects of the condition. The counsellor can help the couple understand what tests may be available during the pregnancy and what management is available after birth and provide supportive counselling.
There will be opportunities for the couple to ask questions and have a full discussion of their concerns.
All prenatal tests can be explained and the results can be further clarified. In some cases, it may be appropriate for further referral to community support groups or other health professionals.