Pregnancy & Genetic Screening

After the anxious and often stressful weeks of undergoing fertility tests and in-vitro fertilization (IVF), it must surely be a joyous moment when the fertilized egg is successfully implanted and both husband and wife are now proud parents-to-be.

However, for couples who are considered to be of high risk when it comes to passing down genetic disorders to their children, it may be worth considering one more round of genetic screening to make sure that their baby is fine.

Dr Wong Pak Seng, a fertility specialist with years of experience and success stories under his belt, says that prenatal genetic screening is still worth considering because no genetic screening is 100% accurate.

Prenatal genetic screening can offer the parents-to-be more peace of mind. Even if the test comes back with unhappy news, the parents-to-be may appreciate having the opportunity to make special arrangements in advance. The parents-to-be also have time to prepare themselves emotionally and make necessary research on how to best provide a special needs child with tender loving care. 

Such screening is recommended for:

• Parents-to-be with a family history of genetic disorders and birth defects.
• Parents-to-be who are aged 40 years or older, especially the mother-to-be, as the risk of having a child with Down syndrome  and other conditions caused by chromosomal disorders is higher.
• Mothers-to-be with abnormal ultrasound findings.
• Mothers-to-be with a history of miscarriages or previous children with birth defects, mental handicap or genetic disorders.

The ‘Old school’ invasive ways

In the past, prenatal genetic screening was done through either amniocentesis or chorionic villi sampling (CVS). Both methods involve the use of needles or other devices to extract samples from the mothers-to-be – hence, the description of these methods as ‘invasive’!

Both methods can cause a certain degree of discomfort and even pain in some mothers-to-be. Furthermore, there is a very small risk of miscarriage, infection and other undesirable complications associated with these procedures. While such complications occur only very rarely, the fact that they can happen drives the medical industry to look for better, less invasive ways to perform prenatal genetic screening.

Fortunately, in the recent years we have developed the technology and method for a less invasive method for prenatal genetic screening. This method is called, appropriately enough, non-invasive prenatal screening test, or NIPST for short.

NIPST – A less invasive solution

Dr Wong explains that, during a NIPST, the doctor only needs to obtain blood sample from the mother-to-be. There are two NIPST services commonly offered by fertility centres in Malaysia.

Non-invasive prenatal diagnosis (NIPD)

When a woman is pregnant, some of her child’s DNA finds its way into her bloodstream. NIPD analyse this DNA for birth defects and genetic disorders such as Down syndrome, Edwards syndrome and Patau syndrome, as well as chromosomal disorders such as Turner syndrome, Klinefelter syndrome and Triple X syndrome.

• When to do it? NIPD can be done from as early as week 9 of one’s pregnancy, but please consult a gynaecologist or fertility specialist for the best time to take this test.
• Accuracy. NIPD is considered to be more accurate than the other available prenatal genetic screening methods available at the moment.
• Risks. Because NIPD only requires a small amount of blood from the mother-to-be, usually extracted from the arm, there is no risk to the mother or the baby she is carrying.
• Expensive? NIPD costs a bit more than many other available methods, as it requires specialised equipment and chemicals to perform the analysis. Currently, fertility centres in Malaysia that offer this service send the blood samples to laboratories abroad for analysis.

First trimester screening (FTS)

FTS is actually a combination of several tests that include ultrasound and blood analysis. It can screen for Down syndrome and heart defects.

• When to take it? FTS is usually performed between week 11 and 14.   
• The procedure. An ultrasound exam will be performed to check the size of the clear space in the tissue found at the back of the baby’s neck (nuchal translucency). Blood tests will be taken and analysed for the levels of two substances: pregnancy-associated plasma protein-A (PAPPA) and human chorionic gonadotropin (HCG).
• Getting the results. The results of the above procedures, along with the age of the mother-to-be, will be used to determine the risk of the child having Down syndrome.
• Risks. There is no known risk associated with FTS.
• Expensive? FTS costs less than NIPD, but its scope of detection is narrower and is slightly less accurate than NIPD. However, it is still a powerful genetic screening procedure worth considering for couples who find NIPD above their budget.

Dr Wong reminds us that these screening tests are not 100% accurate. A low-risk result will not guarantee that the baby will be free from genetic disorders, just like how a high-risk result does not necessarily mean that the child will have a genetic disorder. In some cases, the gynaecologist or fertility specialist may recommend follow-up screening tests to verify the results of these tests.

At the end of the day, the choice to go for genetic screening lies ultimately in the hands of the couple, says Dr Wong. If the couple does not wish to proceed with genetic screening, they are certainly free to do so. The genetic counsellor is always available to offer advice and support if the couple encounter difficulties in making a decision.

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