Prenatal Testing and Amniocentesis
Amniocentesis is a prenatal testing investigation carried out between the 15th and the 12th week of pregnancy, later than chorionic villus sampling– another prenatal test which is carried out earlier in pregnancy. The test is typically called a screening test and carried out to confirm whether the unborn baby is suffering from any genetic/ chromosomal abnormities.
Conditions which are check for with amniocentesis include chromosomal abnormalities: Down’s syndrome, Trisomy 18 and Fragile X syndrome It is also used to check for Neural Tube defects or any uterine infections, to gauge the maturity of the baby’s lungs and their proper development- this especially important if doctor’s think there might be the possibility of a premature delivery.
With regards genetic disorders, there are hundreds of these that amniocentesis can help trace, including Sickle cell.
Because amniocentesis allows access to the child’s DNA, the sample of amniotic fluid taken is also used for prenatal paternity testing.
What is amniotic fluid and why is it important?
Amniotic fluid surrounds the unborn baby in the womb and provides indispensable nourishment to the baby. At the beginning of pregnancy, the fluid is mainly water contain electrolytes. The liquid is clear though can appear slightly yellowish and is contained in the amniotic sac. The baby constantly swallows and “inhales” the fluid and then “exhales” the fluid through urine. The amniotic fluid does in fact also contain urine.
The amniotic fluid help the baby move in the womb- this ensures healthy bone development. It also helps in the development of the lungs.
What happens during amniocentesis?
The investigation is carried out under localized anesthetics, sometimes an anesthetics cream is simply applied to the belly. The OBYN will carry out an ultrasound to gauge the position of the baby in the womb. Once he or she has determined this, a needle will be inserted through the abdomen and into the womb. The OBGYN usually withdraws around 20ml of amniotic fluid. The procedure is quite short and does not take up too much time.
You will not need to undergo amniocentesis or CVS to determine the sex of the baby. An ultrasound after the 14th week done as routine check will also be able to indicate the sec of the baby. You can also opt for a baby gender prediction test in your 9th week using a maternal urine sample.
What are the risks of prenatal testing and amniocentesis?
Unfortunately, amniocentesis does have certain risks which you will be made fully aware of before undergoing the investigation. The risk of miscarriage is the most serious but also extremely unlikely. This might happen because the procedure might stress the unborn child or in some cases, leakage of amniotic fluid endangers the life of the child is levels fall to low to provide oxygen and nourishment to the child. The issue is that some women miscarriage naturally in their second trimester which is the time when an amniocentesis is carried out. Because of this issue, doctors will not be able to know in many cases whether the miscarriage was due to amniocentesis.
Paternity testing and Amniocentesis
Amniotic fluid is rich in fetal DNA. With a sample of amniotic fluid, it is possible to extract the baby’s genetic profile from the DNA found within. Paternity testing with amniotic fluid offers extremely high success rates but there are of course, the inherent risks which worry many expectant mothers. Nowadays, non invasive prenatal testing has been developed which means a simple blood draw of the mother’s blood is enough to map the child’s genetic markers. Amniocentesis and other prenatal testing procedures will likely be used less in future.