Dr Shadab Asst Professor Department of Zoology AMU

Dr. Shadab Asst. Professor Department of Zoology AMU, Aligarh

What is Amniocentesis? ? • A procedure performed usually in the beginning of pregnancy to detect chromosomal abnormalities in the fetus. • Usually done when a woman is between 16 and 22 weeks pregnant. • During this procedure a sample of amniotic fluid is taken from the amniotic sac (amnion) surrounding the unborn baby and its DNA is examined for genetic abnormalities. • The amniotic fluid - has cells that the skin of the developing baby has shed, as well as his/her waste products. Each cell from the baby in the fluid contains their complete set of DNA (genetic information). Analyzing these cells helps the doctors assess the fetus' health and detect any potential problems. • The entire amniocentesis appointment lasts approximately 45 minutes- most of which involves a detailed ultrasound examination.

Who is a candidate for amniocentesis? • Any pregnant woman who, at her due date, will be 40 years of age or older. • Any woman whose Combitest® results are high risk (blood tests and/or fetal ultrasound). • Any woman whose ultrasound results indicate a potential fetal chromosomal anomaly. • Any woman who has a family history or whose partner has a family history of one or more incidents of chromosomal anomalies or genetic disorders with a high recurrence risk. • It is also possible for women under the age of 40, with no history of genetic disorder to have an amniocentesis; it is a matter of personal choice.

What can be detected through an Amniocentesis? • Nearly all chromosome disorders, including Down’s Syndrome as well as sex chromosome abnormalities (such as Turner syndrome and Klinefelter syndrome). • Several hundred genetic disorders, such as cystic fibrosis and sickle cell disease. The test is not used to look for all of them, but if your baby is at increased risk for one or more of these disorders, in most cases amniocentesis can usually tell you whether he has the disease • Neural tube defects such as spina bifida. • Amniocentesis is the only way to obtain information about fetal lung maturity.

• In order to understand amniocentesis it is important to know about certain parts of the body and how they work. . AMNIOTIC SAC AMNIOTIC FLUID UMBLICAL CORD PLACENTA

• Adviced to rest for 24 hours • No strenous work, exercise for 72 hours • No air travel for 72 hours • Seek urgent medical attention if – üfeeling shivery. üHigh fever of 38 degree celcius or above. • Persistant lower back pain and abdominal pain. • After the amniocentesis procedure, the sample of amniotic fluid (the fluid that surrounds the unborn baby in the womb) will be taken to a laboratory for testing. • There are two different types of tests: • a rapid test • a full karyotype

• A rapid test looks for abnormalities on specific chromosomes (the parts of the body’s cells that carry genes). A rapid test can identify a number of chromosomal conditions that cause physical and mental abnormalities. These are: • Down's syndrome – caused by an extra chromosome 21 • Edward's syndrome – caused by an extra chromosome 18 • Patau’s syndrome – caused by an extra chromosome 13 • The results of a rapid test should be ready after three working days. This test is almost 100% accurate, but it only tests for the three conditions listed above.

• Each cell in the body contains 23 pairs of chromosomes. A full karyotype checks all of these. • The cells in the sample of amniotic fluid are grown for up to 10 days in a laboratory before being examined under a microscope to check for: • the number of chromosomes • the appearance of the chromosomes • Results from a full karyotype will usually be ready in two or three weeks. In about 1 in every 100 tests, the results may not be clear. This could be due to the mother’s blood contaminating the sample of amniotic fluid, which may have prevented the cells from growing properly.

• After amniocentesis, the sample of amniotic fluid is sent to a lab for analysis. • Results usually take 10 days to 3 weeks, depending on the lab. • It takes that long to get results because the cells have to grow in the lab in order to analyze them. • In the lab, genetic and chemical tests are done. • For genetic tests, certain chromosomes and genes are analyzed. • For chemical tests, proteins, minerals and other compounds in the amniotic fluid are analyzed. • Amniocentesis results will either be positive or negative.

Negative test results Positive test results • For most women who have amniocentesis, results of the procedure will be ‘negative’. That is, their baby will not have any disorders that were tested for. • If the test result is ‘positive’ it means the baby has the disorder that was being tested for. One should be aware that there is no cure for the majority of chromosomal conditions, so she needs to consider her options carefully. • It is possible to have a negative result from amniocentesis but the baby may still be born with the condition tested for or another chromosomal condition. This is because a normal test result does not exclude every chromosomal disorder. • Options may include: • continuing with her pregnancy while getting information and advice about the condition so she is prepared for caring for her baby. • ending her pregnancy • Options for ending her pregnancy will depend on how many weeks pregnant she is when making the decision.

• It is important to be aware of the possible complications during or after amniocentesis. These are outlined below. Miscarriage Club Foot Rhesus disease • There is a small risk that amniocentesis can cause a miscarriage (the loss of the pregnancy). The risk is estimated to be around 1 in 100. • Amniocentesis may cause club foot in your baby. This is when the baby is born with a deformed ankle and foot. However, the likelihood of this happening is higher if you have amniocentesis before week 15 of your pregnancy. • Rhesus disease is a condition where proteins in a pregnant woman’s blood attack her baby's blood cells. • Rhesus disease is only possible if the mother’s blood is rhesus-negative and the baby's blood is rhesus-positive. If this is the case, amniocentesis could trigger rhesus disease if the mother’s blood is exposed to the baby’s blood during the procedure.

Injury from needle • During amniocentesis, the placenta (the organ that links a pregnant woman's blood supply to her unborn baby's) may be punctured by the needle. Sometimes this is necessary to access the amniotic fluid. If this happens, the puncture wound usually heals without any more problems developing. • Ultrasound (where high frequency sound waves are used to create images) is now commonly used to guide the needle. This significantly reduces the risk of injury. Infection • In very rare cases, an infection may develop if the procedure introduces bacteria in the amniotic sac (the sac surrounding the fetus that contains amniotic fluid). This can cause: • a high temperature (fever) of 38ºC (100. 4ºF) or above • tenderness of abdomen (tummy) • contractions (when your abdomen tightens then relaxes) • One should seek medical attention if she has any of these symptoms. The risk of developing a serious infection from amniocentesis is estimated to be less than 1 in 1, 000.

• Amniocentesis is a safe procedure that can provide helpful information about the health of a fetus. It may be offered to woman who are at a higher risk of having a baby with a genetic disease. The risk of miscarriage of amniocentesis is about 0. 5%, or 1 in 200. • It is the patients decision whether the benefits of the procedure outweigh the risks.

*References: *1. Dev. Biol- Verma and Agarwal *2. Dev. Biol- Wolpert *3. Dev. Biol. - Gilbert *4. Embryology- Ballinsky *5. Wikipedia *6. Freely available resources on internet