It's in the genetics

Dr Priya Kadam tells us why genetic testing is a must during pregnancy

Pregnancy for women marks the beginning of a new stage in their lives. Like any other parent, Juhi (name changed) was excited when she learned about her pregnancy. She had suffered a miscarriage previously as her foetus was affected by down syndrome. While consulting with a geneticist, she was advised of a few options that included a non-invasive prenatal test (NIPT) to help screen for down syndrome and a few other chromosomal disorders. She chose NIPT and waited anxiously for the results. The results arrived soon enough, and it was observed that Juhi’s baby had a very low or negligible risk of having a serious chromosomal disorder. A few months later she delivered a healthy baby girl. Juhi was elated with the outcome and also understood the value of a genetic test and now advises all her relatives to undergo a prenatal screening test. A non-invasive prenatal screening test provides expecting parents with reliable information about their baby’s genetic makeup. Such information is vital to expectant parents for thought-through early pregnancy decisions and to avoid the distress caused by the birth of an abnormal baby unexpectedly.

What are chromosomal
disorders?

The human genetic material consists of 23 pairs of chromosomes. Therefore, any change in this number, wherein extra gain or loss of chromosome can lead to a serious disorder. The most common of these disorders are, Trisomy 21, Trisomy 18 and Trisomy 13, in the population. The estimated risk incidence of a baby with a chromosomal disorder is 1:166 births. Therefore, standard pregnancy care involves early screening for serious chromosomal abnormalities.

Genetic screening tests allow for identifying the genetic disorders or potential risks that the unborn baby may carry. NIPT (Non-Invasive Prenatal Test) has brought precision to the practice of diagnosis. With the advancement in technology, tests have been developed that are safe for the foetus and non-invasive. The non-invasive prenatal screening test can screen for common chromosomal abnormalities such as Trisomy 21(Down syndrome), Trisomy 18 (Edward syndrome), Trisomy 13 (Patau syndrome) and certain other abnormalities like monosomy X (Turner’s syndrome). There are three main reasons why couples should opt for a test:

It helps identify foetuses at risk of serious chromosomal abnormality.

Leads to better management by providing early information.

Prepares for birth and early intervention wherever possible.

Who needs to get tested?

Non-invasive prenatal testing can be recommended to any pregnant woman but is usually recommended when:

The woman is above 30 years of age. Maternal serum screening provides abnormal results.

Certain abnormalities during the ultrasound are identified.

There is a family history of chromosomal conditions or congenital disabilities.

Couples have had a child with a chromosomal disorder.

A couple has a history of infertility or pregnancy loss.

Genetic testing of the pregnancy remains important as pregnancy is a time-sensitive period. When the general pregnant population is screened, most pregnancies eventually have a low risk of these conditions. However, about 2-3% of the tested population by NIPT, receive a high–risk result which requires follow up confirmatory testing through invasive procedures.

(The author is an expert at reproductive genomics.)