What Is Amniocentesis?

An amniocentesis is a prenatal test that allows your fetal medicine specialist to extract a sample of amniotic fluid from the uterus to diagnose chromosomal abnormalities in the baby.

The amniotic fluid contains skin cells shed from the baby and can diagnose chromosomal abnormalities such as Down syndrome.

Amniocentesis produces a karyotype – a picture of the baby’s chromosomes – to determine any abnormalities. (In about 1 percent of cases, there’s a problem with the specimen, and the test doesn’t yield a result.)

Amniocentesis is usually done when a woman is between 16 and 20 weeks pregnant. Though all women have the option of having an amniocentesis, women for whom this test is recommended are often those at increased risk for genetic and chromosomal problems. The test is invasive and carries a small chance of miscarriage (0.01%)

Best Amniocentesis Testing Center in Chennai

Chennai Women’s Clinic offers amniocentesis services under the care of Dr Deepthi Jammi, an award winning Obstetrician and Gynaecologist in Chennai. Here, we take the utmost care to keep yourself and your baby’s safety as our priority.

How Is Amniocentesis Performed?

The procedure usually takes about 15 minutes. Before the process, an ultrasound is done to measure the baby and check the basic anatomy.

The abdomen is cleaned with a sterile solution to minimize infection risk for the procedure itself. Then, ultrasound is used to pinpoint a pocket of amniotic fluid safe from both the baby and the placenta. This part can take up to 10minutes.

Then, under continuous ultrasound guidance, the doctor inserts a long, thin, hollow needle through the abdominal wall and into the sac of fluid around the baby. The doctor withdraws a small amount of amniotic fluid and then removes the needle. Sometimes, not enough fluid is removed the first time the needle is inserted. If this happens, the needle will be inserted again. Withdrawing the fluid can take a few minutes but usually takes less than 30 seconds. The baby will make more fluid to replace what’s taken out.

The amniotic fluid, which contains cells shed by the baby, is sent to the laboratory for analysis. The first level of reporting (initial confirmation) will be available in 10 to 15 days, and the final report will be available in 4 weeks.

Afterwards, the doctor may use an external fetal monitor to listen to the baby’s heartbeat for reassurance.

Amniocentesis Procedure
Amniocentesis Procedure

Why is Amniocentesis Recommended?

It may be recommended for the following reasons:

  • Suppose the patient is 37 years or older. Anyone can have a baby with a chromosomal abnormality, but the risk rises with the mother’s age. For example, the likelihood of carrying a baby with Down syndrome increases from about 1 in 1,200 at age 25 to 1 in 100 at age 40.
  • A pregnancy screening test has suggested there may be a problem, such as Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. 
  • The mother has had a previous pregnancy with these problems with Trisomy 21, 13 or 18.
  • An abnormality is detected in the baby during a routine ultrasound scan.
  • To diagnose or rule out an intrauterine infection.
  • If too much amniotic fluid is accumulated (polyhydramnios), amnio reduction might be made to drain excess amniotic fluid from the uterus.

Is Amniocentesis Painful?

Amniocentesis isn't usually painful, but the patient may feel cramping, pinching, or pressure and uncomfortable during the procedure.

Some women describe experiencing a pain similar to period pain or feeling pressure when the needle is taken out.

The amount of discomfort or pain varies among women and even from one pregnancy to the next.

How Long Does It Take?

The procedure usually takes around 15 minutes to perform.

Afterwards, the patient will be monitored for up to an hour if the test causes any side effects, such as heavy bleeding.

Estimates vary, but research suggests that the loss rate from the procedure is around 1 in 100 to 200.

What Disorders And Defects Can Amniocentesis Detect?

Amniocentesis is used to detect nearly all chromosomal disorders, including Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities (such as Turner syndrome). However, while the test can diagnose these conditions, it can't measure their severity.

It can also detect several hundred other genetic disorders, such as cystic fibrosis, sickle cell disease, and Tay-Sachs disease. The test is not used to look for all of them, but if the baby is at increased risk for one or more of these disorders, amniocentesis can usually tell whether the baby has the disease.

What Is The Risk Of Miscarriage From Amniocentesis?

The risk of miscarriage due to amniocentesis is low. Because a certain percentage of women will end up miscarrying in the second trimester anyway, there's no way of knowing for sure whether the procedure actually caused a miscarriage following an amniocentesis. Estimates vary, but research suggests that the loss rate from the procedure is around 1 in 100 to 200.

Before the patient decides to have amniocentesis, the doctor will convey the risks and possible complications.

Some Other Risks Include

There are also some other risks, such as infection or needing to have the procedure again because it wasn’t possible to test the first sample that was removed accurately.

The risk of amniocentesis causing complications is higher if it’s carried out before the 15th week of pregnancy, which is why the test is only carried out after this point.

How Can The Patient Decide What's Right For Her?

First and doctors can only recommend second-trimester screening and diagnostic testing options, but whether or not to test is a personal decision of the mother and her family.

Some possible choices are:

  • Opt for ultrasound-based screening and then decide on diagnostic testing (invasive procedures) based on the initial results.
  • Undergo diagnostic testing right away.
  • Have no screening or testing.

If the patient opts for screening first, she can then decide — with the doctor’s help — whether the results indicate a high enough risk that a CVS or amniocentesis is required to confirm whether a problem exists. The patient will need to weigh the need to know about the baby’s condition against the small chance that diagnostic testing could cause a miscarriage.

A few conditions may be detected while the baby is still in the womb. So if there’s a strong suspicion that the baby may have one of these rare problems, an amniocentesis can help find out.

Recovering After Amniocentesis

After amniocentesis, it’s normal to have cramps similar to period pain and light vaginal bleeding called “spotting” for a day or two.

It is advised to avoid any strenuous activity for a few days following the procedure.

However, the patient should contact the obstetrician in case of the following symptoms:

Frequently Asked Questions

A positive result suggests that the fetus has the genetic problem tested for. In this cas, your doctor will discuss the results with a genetic counsellor. They can help you understand the problem, talk to you about your options, and help you decide what to do next.

Genetic amniocentesis is usually performed between weeks 15 and 20 of pregnancy. It is known that amniocentesis done before week 15 of pregnancy is associated with higher rates of complications.

There is a small risk associated with your baby during amniocentesis. This is approximately less than 1%. Other very rare complications can be injury to the baby or mother, infection, and preterm labor.

Amniocentesis gives a definitive result. It has a reliable rate of 98%. However, it can’t pick all genetic problems or other abnormalities

The test checks for fetal abnormalities (birth defects) such as Down syndrome, cystic fibrosis or spina bifida. Other genetic problems, or neural problems, and Rh incompatibility cannot be detected by amniocentesis. Talk to your doctor to be well informed before the procedure.

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