It may be recommended for the following reasons:

• If 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 rises from about1 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), amino reduction might be done to drain excess amniotic fluid from the uterus.

Amniocentesis is used to detect nearly all chromosomal disorders, including Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities (such as Turner syndrome). 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.

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 a miscarriage following an amniocentesis was actually caused by the procedure.

Estimates vary, but research suggests that the loss rate from the procedure is around 1 in 500.

Before the patient decides to have amniocentesis, the risks and possible complications will be conveyed by the doctor.

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

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.

Other risks include

• Cramps after the procedure.
• Small amount of vaginal bleeding after the procedure.
• Rarely, amniocentesis may cause amniotic fluid to leak.
• Another rare complication is a uterine infection. A serious infection happens in about 1 in 1000 women (0.1%).
• If the mother has an infection such as Hepatitis-C or HIV, amniocentesis can cause the infection to transfer to the unborn baby.
• Needle injury - during amniocentesis the baby might move an arm or leg into the path of the needle. Serious needle injuries are rare and is usually taken care of since it is ultrasound guided procedure.
• Rh sensitization - rarely, amniocentesis might cause the baby's blood cells to enter the mother's bloodstream. If the mother has Rh negative blood and has not developed antibodies to Rh positive blood, the mother will be given an injection of a blood product called Rh immune globulin after amniocentesis. This will prevent the body from producing Rh antibodies that can cross the placenta and damage the baby's red blood cells. A blood test can detect if the mother has begun to produce antibodies.

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

For the procedure itself, the abdomen is cleaned with sterile solution to minimize the risk of infection. Ultrasound is used to pinpoint a pocket of amniotic fluid a safe distance 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 with drawing 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. First level of reporting (initial confirmation) will be available in 10 to 15 days and the final report will be available in 4 weeks time.

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

Amniocentesis isn't usually painful, but the patient may feel uncomfortable during the procedure.

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

The patient may sometimes feel some cramping, pinching, or pressure during the procedure. The amount of discomfort or pain varies among women and even from one pregnancy to the next.

The procedure usually takes around 15 minutes to perform.

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

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 obstetricianin case of the following symptoms:

• persistent or severe pain
• a high temperature of 38C (100.4F) or more chills or shivering
• discharge or clear fluid coming from the vagina
• contractions (when your abdomen tightens then relaxes)
• Loss of vaginal fluid or vaginal bleeding
• Severe uterine cramping that lasts more than a few hours
• Redness and inflammation where the needle was inserted
• Unusual fetal activity or a lack of fetal movement