13 April 2010
By Sumitra Deb Roy
For the Chabrias, getting pregnant was a traumatic experience after four miscarriages. They were lucky in their fifth attempt–Raunak carried their son to full term: but the child was diagnosed with multiple congenital malfunctions. It was found that the father’s chromosomal abnormalities were behind the failed pregnancies and their son’s medical problems. The Chabrias are part of an ongoing study conducted by a city laboratory and involving 6,750 Indian couples who have a history of miscarriages. The study found that chromosomal abnormalities can be blamed for reproductive failure or the birth of malformed children in many cases.
The study shows that 3.3% of the couples had major chromosomal abnormalities, around 6.2% had minor abnormalities. It was this that resulted in repeated loss of pregnancy and the birth of deformed children. “Globally, there is a belief that as many as 60% of miscarriages in the first trimester could be due to a chromosomal abnormality in either of the parent,” said Dr Swarna Mandava, cytogenetics, Religare SRL diagnostics.
Chromosomes carry information about one’s genetic makeup. Chromosomal abnormality arises when these building blocks are extra, missing, broken or even arranged in the wrong order and are passed on to the children at the time of conception. The study, conducted over the last seven years, was recently presented at the National Conference of Indian Society for Pre–Natal Diagnostics and Therapy. “Among the major chromosomal aberrations, 58.7% cases were found in women and 41.3% in men,” said Mandava.
These figures underline the importance of chromosome study in cases of “familial structural abnormalities and frequent pregnancy loss”. So, if you have a history of miscarriage it would be in the best interest of the family to take a cytogenetic test. In another couple–first cousins–it was found that both had the same type of ‘balanced translocation’ where a piece of a chromosome had broken off and attached itself to another one. When individuals cells divide to create egg or sperm cells for reproduction, the egg or sperm cells can end up with the missing genetic material. Balanced translocations accounted for 22% of abnormalities.
According to Mandava, many gynaecologists are now referring patients to genetic counsellors. While tests that can reveal if a newborn will be healthy or not, they come with a caveat: they entail some chances of miscarriage. Yet, experts say they are necessary evils. “Tests like a triple marker can show if the child has any abnormality and eventually the couple can choose to go for per–natal testing.” said Dr Adi Dastur, dean of Wadia Maternity Hospital and gynaecologist.
Some pre–natal screenings can also pick up structural defects in the unborn child. “In such cases, a child can be immediately operated on birth if the defect is repairable,” said Dr Vivek Rege, paediatric surgeon, Breach Candy Hospital.
Beyond prevention, the technology to rectify these abnormalities is still in its infancy. But just because you have a defective chromosome, it does not mean that your child’s fate is sealed. It depends on whether that particular chromosome plays a part in the conception of the foetus. “Not every couple with a chromosomal defect will end up having miscarriages or malformed children. Only in those with major chromosomal disorders do the chances go up to 70–75%,” said Dastur.
- A study that tested 6,750 couples with a history of miscarriages and/or birth of children with congenital defects found that in many cases chromosomal abnormalities in either of the parent were the culprits
- 3.3% of the test couples had major chromosomal abnormalities
6.2% had minor abnormalities
Among the major chromosomal aberrations detected, 58.7% cases were found in women and 41.3% in men
Chromosomes are made of DNA and contain all information about our genetic makeup
Humans have 46 chromosomes
Complications arise when the chromosomes are extra, missing, broken or even arranged in the wrong order and are passed on to the children at the time of conception
Chromosome disorders can manifest in various ways starting from miscarriages to the child having Down’s syndrome, Patau’s syndrome, etc
What can couples do?
If there is a history of chromosomal abnormalities in the family, seek help from a genetic counsellor
If you suffer from miscarriages or have a child with genetic abnormalities, get a chromosomal analysis to ensure that later pregnancies are risk–free
Taking a cytogenetic test
Couples have to provide blood samples
Cells are cultured, dyed and viewed under a microscope
Cost ranges from Rs 2,000 to Rs 3,000
- A young couple had a history of one miscarriage and 3 neonatal deaths due to congenital malfunctions. On examination, the husband had showed a unique type of chromosomal insertion–addition of more pairs to the DNA sequence.
- Tests on a couple–first cousins–with a history of miscarriages, showed that both had balanced translocation where a part of a chromosome has broken off and attached itself to another location.
- In a city couple with a history of two miscarriages and two malformed children, the husband showed normal chromosome appearance but the wife had abnormalities.