Navigating the complexities of genetic testing during pregnancy is crucial for parents seeking a deeper understanding of potential chromosomal abnormalities. Invaluable insights, factors influencing risks, and the significance of genetic counseling are important in making an informed decision. Early detection through non-invasive prenatal testing offers families options for proactive pregnancy management, empowering them with the knowledge to navigate the journey of parenthood. Dr Priya Kadam, Director, Reproductive Genomics, MedGenome answers how genetic tests for prenatal and postnatal healthcare influence decision-making and counseling for families at increased risk of chromosomal abnormalities
1. How can genetic tests help to understand if you are at higher risk of having a baby with Down syndrome or other chromosomal problems?
The anticipation of potentially having a child with a congenital or genetic disability is a significant concern for any expectant parent. Every parent wants their child to be healthy and normal. Unfortunately, statistics reveal that around 2.5 percent of infants are born with congenital anomalies, contributing to 8-15 percent of perinatal deaths and 13-16 percent of neonatal mortality in India . Among these cases, 1-2 percent are identified as having chromosomal anomalies. These anomalies result from missing, extra, or irregular segments of chromosomes.
Down Syndrome is the most common chromosomal problem seen in newborn babies. It affects approximately 23,000-29,000 children born in India every year. Parents of these children are genetically normal; the extra chromosome occurs by random chance. Screening for common chromosomal abnormalities is recommended by all obstetrics and fetal medicine societies and if an abnormality is found to further test for conformation of findings. One useful screening test is non-invasive prenatal testing.
The International Society for Prenatal Diagnosis (ISPD) recommends Non-Invasive Prenatal Testing (NIPT) as the primary screening for chromosomal abnormalities in pregnant women. NIPT, effective from the ninth/tenth week of gestation, boasts a 99.84% accuracy and negative predictive value, sparing women unnecessary invasive tests. Non-Invasive Prenatal Screening (NIPS), especially NIPT, is able to detect extra copy or a loss of any of the twenty-three chromosomes as well as some methods are able to detect microdeletions, small chromosome portion losses, often go unnoticed during pregnancy, causing severe physical and/or intellectual impairments.
Early detection of Down Syndrome through prenatal genetic testing aids timely identification, enabling parents to make informed decisions on disease management and caregiving options. Early intervention and support services enhance the functioning of children with Down syndrome. More tests like Carrier screening, Karyoseq also provide information into the genetic composition of both parents and the developing fetus, aiding in early detection and informed decision-making during pregnancy.
Genetic tests such as FISH/aneuploidy screening by QF-PCR provide a quick result of these chromosomal abnormalities while microarray as well as next generation sequencing can give further detailed information about the fetus, that can give used as and when appropriate based on prenatal ultrasound findings, family history, prior tests, and parental carrier status.
Carrier screening performed before conception or early prenatal scenario can help identify potential risk of transmitting genetic disorders through both parents, aiding informed decisions about pregnancy.
2. What factors contribute to this risk, and how accurate are the tests?
The risk of genetic abnormalities in a pregnancy can be influenced by various factors, including maternal age, family history of genetic disorders, and certain medical conditions. Advanced maternal age, particularly for women over 35, is a major factor associated with an increased risk of chromosomal abnormalities, such as Down syndrome.
NIPT screens for abnormalities in the foetus by testing the mother’s blood just like in a blood test. The risk of having these disorders is very accurately detected by this test.
MedGenome’s KaryoSeq – a low pass whole genome sequencing, is a faster and accurate solution which allows for the detection of small chromosomal abnormalities, such as microdeletions or micro duplications. It is recommended for individuals with suspected or confirmed genetic disorders or an increased risk of carrying chromosomal abnormalities, aiming to provide precise and rapid results, and helping clinicians and families make informed decisions about inherent genetic conditions.
3. If the tests show an increased risk, what options are available for further testing or pregnancy management?
Genetic counseling is a crucial step in the process, offering comprehensive support and guidance. A genetic counselor can help individuals understand the implications of the test results, discuss available options, and provide emotional support during this challenging time.
If screening test show abnormalities, further testing such as amniocentesis can be recommended, and options be discussed with the couple.
Based on the results and the information provided by genetic counseling, individuals can then make informed decisions regarding pregnancy management. Options include continuing the pregnancy with appropriate medical care, preparing for potential challenges, or in certain cases, considering the option of termination if life-threatening abnormalities are identified.
4. If a baby is diagnosed with a chromosomal condition, what does that mean for their health and development? What additional tests or screenings might be recommended?
There are several kinds of genetic conditions that occur due to chromosomal disorders such as down syndrome, Klinefelter Syndrome, Turner Syndrome, Rett Syndrome, Trisomy 13 etc and the children can experience developmental delays, behavioural changes, cognitive defects, limb or facial anomalies, movement disorders etc.
Other problems could be microdeletion and micro duplications or single gene disorders for which arrays and next generation sequencing can be recommended based on the specific condition that is suspected.
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