We as parents like to give our baby everything perfect – the perfect clothes, school, food, family etc. But there are some tiny things that slip out of our control and there is nothing we can do about them. Like the genes your baby inherits from you. Slight tweak here could lead to an unfortunate turn of events. But now there is something you can do about it too. Prenatal Genetic Diagnosis.
It is a screening procedure designed to identify couples having a greater risk of having babies with genetic abnormalities. After a detailed analysis of your family and reproductive history and possible environmental factors, we counsel you and your husband to make a unified decision regarding the future management of pregnancy.
Should you get a screening done? Yes, if any of the following applies to you
- Age more than 35 years
- Family history of neural tube defects
- Previous baby born with neural tube defects
- Previous child with chromosomal anomaly
- One or both parents – carries of sex linked or autosomal traits
- History of recurrent miscarriage
During pregnancy :
- Too less (oligohydramnios) or too much (polyhydramnios) of amniotic fluid
- Severe restriction in the growth of fetus
- Abnormal ultrasound findings
- Uncontrolled diabetes in early pregnancy
- Contact with infection like rubella, cytomegalovirus
- Intake of harmful drugs like methotrexate (teratogenic drugs)
- Abnormal screening for mother ‘s blood
Any woman who comes to us for prenatal genetic diagnosis is first counselled and informed about the procedures to be done with her prior consent.
How do we go about it?
So we carry out this screening under three major heads :
- Biochemical :
This category includes testing for markers present in the mother’s blood, baby’s blood or the amniotic fluid at specific weeks of pregnancy. It includes :
- MSAFP ( maternal serum alpha fetoprotein )
- Triple test
- Quadruple test
- Acetylcholine esterase (AchE)
- Biophysical :
This includes visualising the baby in the womb under an ultrasonography scan to identify physical features suggestive of genetic anomalies. We look for a lot of biophysical markers, the most important ones being :
- Crown-Rump length
- Nuchal translucency
- Nasal bone
- Cytogenetic :
This is an interesting but a slightly risky category wherein we extract the foetal tissue to culture it and test it for a tweaked DNA signalling a defect in the genetic composition of the baby. Since we need to reach out to the baby to collect a few sample cells, it includes invasive procedures like :
- Chorionic villus sampling
Women who usually test positive for this screen are offered fetal karyotyping. Karyotyping is like taking a photograph of your genetic package. The chromosomes are seen for their size, shape, number etc. A too large chromosome or a shortened arm of a chromosome, too many chromosomes or a missing chromosome can all be seen to know where exactly the problem lies. This helps your doctor to counsel you and guide you towards the best management for your pregnancy and baby.