The reasons why
There are many reasons why a couple, or parent-to-be, may be referred to a genetic counselor during a pregnancy.
These include:
- Maternal age
Maternal age is a known risk factor in the development of specific genetic syndromes. The older the age of the mother, for example, the higher the risk of having a baby born with Down syndrome. A mother-to-be, over the age of 35, may be referred to a genetic counselor to understand the risks and genetic testing options available, especially for syndromes where a higher maternal age is a known risk factor.
- Family history of rare disease
A family history of a rare disease may place future children at risk of developing the same syndrome. Genetic counseling would be recommended to all those with a family history of inherited conditions, regardless of whether the parents are known to be carriers or not. In these cases, a genetic counselor will explore the full family medical and genetic history and what this might mean for new parents.
- One or both parents are carriers of a gene mutation
If one or both parents are known to be carriers of a specific gene mutation or chromosomal abnormality, genetic counseling will be recommended both before and during pregnancy. This is to ensure the parents understand the risks involved in passing on an inherited genetic condition to their child.
Parents who are carriers of a changed gene may pass rare diseases onto their children in several ways depending on the specific mode of inheritance:
If both parents carry one copy of each of the mutated genes, the risk is that they will pass these copies onto their child, and trigger an autosomal recessive genetic syndrome, such as Tay-Sachs disease.
Autosomal recessive inheritance means an affected individual receives one copy of a mutated gene from each of their parents, giving them two copies of a mutated gene. Parents, who carry only one copy of the gene mutation will not generally show any symptoms but have a 25% chance of passing the copies of the gene mutations onto each of their children.
For other syndromes, inherited in an autosomal dominant inheritance are caused by just one copy of the gene mutation. In the case of autosomal dominant inheritance, just one parent is the carrier of the gene mutation, and they have a 50% chance of passing it on to each of their children.
It is very important for parents who are carriers, to undergo genetic counseling before and during pregnancy, to understand the steps that can be taken to ensure a healthy pregnancy and newborn, dependent on the type of gene mutation they carry.
- Fetal screening showed potential rare disease symptoms
Families, without any history of a rare disease, may be referred to genetic counseling during pregnancy, if standard antenatal screening tests, including ultrasounds, reveal possible symptoms of a rare disease. Sometimes characteristics of facial features of a rare disease might be identified through ultrasound before birth, as might other symptoms including a failure to thrive, slow growth, or accelerated growth. Macrocephaly (an exceptionally large head), can sometimes be diagnosed by ultrasound before birth, and can also be a symptom of a rare disease.
Any concerns identified during fetal screening would involve referral to a genetic counselor, who can walk parents-to-be through the possible causes of the symptoms, and recommend which genetic tests and further screening would be recommended to either rule out or confirm a diagnosis. A genetic counselor would be able to recommend the most accurate testing options, based on the symptoms found, and the condition suspected.
- Prenatal screening tests (invasive or non-invasive) revealed possible risk for a rare disease
One standard type of prenatal genetic testing is the fetal nuchal translucency test(which measures the fluid buildup behind the neck of a fetus, and specifically its thickness. A thicker-than-normal measurement may be a very early indication of Down syndrome, or trisomy 18.), for example, can show possible signs of a genetic syndrome. They are not able to confirm or diagnose a syndrome.
But if they reveal a potential sign or symptom of a rare disease, genetic counseling will often be recommended, as parents will need to be made aware of the options for more invasive testing, amniocentesis for example, and to understand the risks and benefits involved in such testing.
If further testing, such as amniocentesis (which involves taking a sample of amniotic fluid from around the developing baby), or more advanced and accurate non-invasive prenatal testing (NIPT), confirms a rare disease in an unborn child, then genetic counseling will be essential for parents in terms of understanding what this genetic diagnosis might mean for their child once born, and their options moving forward.
This is a very sensitive, and difficult process during pregnancy, and genetic counseling provides much-needed emotional support, alongside guiding parents through the diagnostic and testing process.
Genetic counseling during pregnancy – what it involves
(and what genetic counseling can tell you)
- Emotional support both during and after a diagnosis
- Knowledge and information and rare diseases, including their causes and possible symptoms
- Information about the options for genetic testing, what each test might involve, and what results might mean
- Coordination of the different medical teams and professionals involved in diagnosis, and managing the care of a rare disease patient
- An interpretation of medical terms and language
- Recommendations for which genetic tests to proceed with, following a diagnosis, possible treatment and care options as well
Genetic counseling has a significant role to play during pregnancy for many families. And as an awareness of rare diseases grows, and as more prenatal genetic screening tests become available, demand for this essential service is expected to grow as well.
