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(Ms Anusree Singapur, MSc Genetic Counseling; Genetic Counselor, Milann Fertility and Birthing Hospital, Bengaluru)
A triple chromosome 21 causes the genetic disorder known as Down syndrome. With several health ramifications, this additional genetic material influences both cognitive and physical development. Couples with a history of genetic conditions or fertility challenges may face increased risks. However, Assisted Reproductive Technology (ART) can be a boon in supporting them on their journey to parenthood.
Understanding why Down Syndrome and Its Genetic Causes
Down syndrome occurs in approximately 1 in 700 births in India. The difficulties in development arises from an extra copy of chromosome 21. Well, the effects vary from person to person. Some may suffer from moderate learning disabilities, while others may suffer from severe health conditions like digestive or cardiac disorders. Whereas, common traits include unique facial features, small stature, and children’s delayed growth. People with learning difficulties struggles in different ways such as with language and memory.
Reasons behind the occurrence of this, include:-
- the random (de novo) error during egg or sperm formation or occasionally during the early stages of embryo development after fertilization,
- advanced maternal age, which increases the risk of non-disjunction that is failure of chromosomes to separate properly,
- inheriting from the parent who is a balanced chromosomal translocation carrier,
- A rare case, where, the child inherits from a parent who is already affected by Down syndrome.
When a parent carries a balanced translocation involving chromosome 21, there’s a risk of passing on an unbalanced form to the child, resulting in Translocation Down syndrome. In these families, the recurrence risk is significantly higher than in the general population, and requires careful reproductive planning.
Balanced Translocation Carriers: Impact on Fertility and Pregnancy Outcomes
A balanced translocation involves the rearrangement of genetic material without any loss or gain. While carriers usually do not have any health issues themselves, their reproductive outcomes can be significantly affected. They are at increased risk for:
- Infertility or repeated IVF failures
- Recurrent pregnancy loss (RPL)
- Having a child with an unbalanced chromosomal condition, such as Down syndrome
Natural conception in such cases often leads to embryos with unbalanced genetic material, leading to implantation failure, miscarriages, or birth defects.
How ART Helps: Pre-implantation Genetic Testing
Modern ART techniques, especially in vitro fertilization (IVF) combined with Preimplantation Genetic Testing (PGT), have been revolutionary for such couples. PGT allows for the selection of chromosomally normal or balanced embryos before implantation:
- PGT-SR(for structural rearrangements) helps detect unbalanced translocations
- PGT-A(for aneuploidy) screens for extra or missing chromosomes, including Trisomy 21
This greatly improves the chances of a healthy pregnancy and minimizes the emotional burden of repeated miscarriages.
Who Can Benefit from ART + PGT?
Couples who may benefit include: carriers of balanced chromosomal translocations, couples with recurrent pregnancy loss or IVF failures, those with a family history of chromosomal disorders, and women of advanced maternal age (35+) at higher risk for Trisomies.
Prenatal Screening & Diagnosis
During the pregnancy phase, the women should consult a doctor and on recommendations only they should undergo any screening or diagnosis.
Hence, down syndrome can arise from a variety of genetic mechanisms—including random events, advanced maternal age, or inherited chromosomal rearrangements. With proper genetic counseling, ART, and PGT, couples at risk can take proactive steps to ensure healthy pregnancies. Personalized reproductive care guided by genetics is key to supporting these families on their parenthood journey.
