Amniocentesis is a highly accurate prenatal diagnostic test that provides crucial, definitive information about your baby's health and development. Unlike prenatal screening tests, which only indicate the probability or risk of a condition, amniocentesis provides a conclusive diagnosis. The procedure involves taking a small sample of the amniotic fluid that surrounds the baby in the womb.

This fluid contains fetal cells that carry the baby's complete genetic blueprint. By analyzing these cells, doctors can diagnose certain chromosomal abnormalities, genetic disorders, and neural tube defects with a very high degree of accuracy. It is an elective procedure, typically offered to expectant parents between the 15th and 20th weeks of pregnancy when there is an increased risk for such conditions.

While the decision to undergo amniocentesis is deeply personal, it is a powerful tool that can provide reassurance, clarity, and essential information to help you and your medical team plan for the healthiest possible future for your child.

What is Amniocentesis?

Amniocentesis is a medical procedure used in prenatal diagnosis. The name is derived from amnion (the membrane surrounding the fetus) and kentesis (the Greek word for puncture). Under the constant guidance of a real-time ultrasound, a specialist physician inserts a very thin, hollow needle through the mother's abdomen into the uterus and amniotic sac to withdraw a small amount of amniotic fluid (typically about 20-30 ml).

This amniotic fluid is a remarkable substance; it is more than just protective cushioning for the baby. It contains living fetal cells that have been shed from the baby's skin and respiratory tract. These cells contain the baby's full set of chromosomes and DNA. The fluid also contains various proteins and substances produced by the baby, such as alpha-fetoprotein (AFP), which can provide information about the development of the baby's spine and brain.

Once collected, the sample of amniotic fluid is sent to a specialized genetics laboratory. There, the fetal cells are cultured (grown) and then analyzed to create a picture of the baby's chromosomes (a karyotype) or to test for specific genetic mutations. The entire procedure is performed with meticulous care to ensure the safety of both mother and baby.

When is Amniocentesis Recommended?

The decision to have an amniocentesis is a choice, and it is usually offered when there is a specific medical reason to seek more definitive information than screening tests can provide. Your obstetrician or a fetal medicine specialist may discuss this option with you in several situations:

• Abnormal Prenatal Screening Test Results: If a first-trimester screening (Double Marker test) or a second-trimester screening (Quadruple Marker test) indicates a high risk for a chromosomal condition like Down syndrome, Edwards syndrome, or Patau syndrome, amniocentesis is offered as the next step to get a definite yes-or-no answer.
   
• Advanced Maternal Age: Women who will be 35 years or older at the time of delivery have a statistically higher chance of having a baby with a chromosomal abnormality. Amniocentesis is offered as a diagnostic option to all women in this age group.
   
• Previous Pregnancy with a Chromosomal Abnormality: If you have had a previous pregnancy affected by a condition like Down syndrome, the risk in subsequent pregnancies is slightly increased, warranting the offer of a diagnostic test.
   
• Known Family History of a Genetic Disorder: If you, your partner, or a close family member has a known genetic disorder (like cystic fibrosis, thalassemia, or sickle cell anemia), or if you are both known carriers of a recessive gene, amniocentesis can determine if the baby has inherited the condition.
   
• Abnormal Ultrasound Findings: If a routine ultrasound reveals certain physical markers or structural abnormalities in the baby's development that are associated with genetic syndromes, amniocentesis can help identify the underlying cause.
   
• Late-Pregnancy Indications (Therapeutic or Maturity Amniocentesis):

Fetal Lung Maturity: If there is a need for a preterm delivery, an amniocentesis can be performed later in the third trimester to test the amniotic fluid for substances that indicate whether the baby's lungs are mature enough to breathe on their own.

Diagnosis of Fetal Infection or Other Illness: The fluid can be tested for infection if there is a concern of chorioamnionitis.

Treatment for Polyhydramnios: In cases where there is an excessive amount of amniotic fluid (polyhydramnios) causing maternal discomfort or complications, a larger volume of fluid can be removed to relieve the pressure.

Understanding the Conditions Amniocentesis Can Detect

Amniocentesis provides a window into the genetic makeup of the fetus. It is primarily used to diagnose:

Chromosomal Abnormalities

These are conditions caused by an incorrect number of chromosomes or structural changes in the chromosomes. Human cells normally have 46 chromosomes, arranged in 23 pairs.

• Down Syndrome (Trisomy 21): The most common chromosomal condition, caused by an extra copy of chromosome 21.
• Edwards Syndrome (Trisomy 18) and Patau Syndrome (Trisomy 13): These are more severe and rarer conditions caused by an extra copy of chromosome 18 or 13, respectively.
• Sex Chromosome Abnormalities: Conditions like Turner syndrome (a missing X chromosome in females) and Klinefelter syndrome (an extra X chromosome in males).

Neural Tube Defects (NTDs)

These are birth defects of the brain, spine, or spinal cord. Amniocentesis can detect these by measuring the level of alpha-fetoprotein (AFP) in the amniotic fluid. High levels of AFP are strongly associated with open NTDs like:

• Spina Bifida: Incomplete closing of the backbone and membranes around the spinal cord.
• Anencephaly: A severe condition where a major portion of the brain, skull, and scalp is absent.
   

Single-Gene Genetic Disorders

Unlike chromosomal abnormalities which involve large-scale genetic changes, these are caused by mutations in a single gene. Amniocentesis can test for thousands of these disorders, but the lab must know exactly what to look for. This testing is only done when there is a known family history or carrier status for a specific condition, such as:

• Thalassemia: A group of inherited blood disorders that affect the body's ability to produce hemoglobin.
• Sickle Cell Anemia: An inherited red blood cell disorder.
• Cystic Fibrosis: A progressive, genetic disease that causes persistent lung infections and limits the ability to breathe over time.

Risk Factors & When to Consider the Test

The conversation about amniocentesis is part of a comprehensive prenatal care journey. You should consider discussing this option in detail with your doctor or a genetic counsellor if any of the indications mentioned above apply to your pregnancy. It is a decision that weighs the need for definitive information against the small but real risks of the procedure.

The process is entirely voluntary, and the goal is to provide you with all the information you need to make the choice that feels right for you and your family.

Our Specialists

The safety and accuracy of an amniocentesis depend heavily on the skill and experience of the performing physician. Our Fetal Medicine units are led by highly trained specialists dedicated to the care of high-risk pregnancies.

Dr. SEEMA THAKUR

SENIOR CONSULTANT FETAL MEDICINE | Fortis Shalimar Bagh

Dr. Jayati Dureja

CONSULTANT FETAL MEDICINE | Fortis La Femme GK

Dr. Joyce Jayasheelan

CONSULTANT OBSTETRICS & GYNAECOLOGY | Fortis BG Road

Patient Stories

“The results from my Double Marker test came back as high-risk for Down syndrome, and we were filled with anxiety and uncertainty. Our doctor explained all the options, and we chose to have an amniocentesis for a clear answer. The procedure itself was quick and much less uncomfortable than I had feared. The fetal medicine team was incredibly professional and reassuring. Waiting for the results was difficult, but when we received the news that the chromosomes were normal, it was an immense relief. It allowed us to enjoy the rest of our pregnancy without that cloud of worry.”  — R. Singh, 36, Gurugram

“My husband and I are both carriers for Thalassemia. We knew there was a 1 in 4 chance our baby could be affected. We decided on amniocentesis to know for sure, so we could be prepared. The genetic counsellor at Fortis was amazing, walking us through every step. The procedure was smooth, and getting the definitive diagnosis allowed us to coordinate with pediatric specialists and plan for the specific care our baby would need right from birth. The knowledge, while difficult, was empowering”.  — A. Khan, 31, New Delhi

The Amniocentesis Procedure: A Detailed Walkthrough

Knowing what to expect can significantly reduce anxiety about the procedure.

Preparation for the Procedure

• Genetic Counselling: Before the test, you will likely have a session with a genetic counsellor to discuss the risks, benefits, and potential outcomes in detail.
• Informed Consent: You will be asked to sign a consent form confirming that you understand the procedure and its risks.
• Timing: The test is typically done between 15 and 20 weeks of gestation.
• Bladder: Depending on the exact timing and position of the uterus, you may be asked to have a full or empty bladder. You will be given specific instructions.
• Rh Factor: Your blood type will be checked. If you are Rh-negative, you will receive an injection of Anti-D (Rh immunoglobulin) after the procedure to prevent complications in future pregnancies.

During the Procedure (Typically lasts about 20-30 minutes, with the needle insertion itself lasting only a minute or two)

• Ultrasound Scan: You will lie down, and a detailed ultrasound will be performed to check the baby's position, the location of the placenta, and to identify a safe pocket of amniotic fluid.
• Site Preparation: Your abdomen will be cleaned with an antiseptic solution to prevent infection.
• Needle Insertion: Under continuous, real-time ultrasound imaging, the specialist will guide a thin, hollow needle through your abdominal wall and into the amniotic sac, carefully avoiding the baby and the placenta.
• Fluid Withdrawal: A syringe is attached to the needle, and a small amount of amniotic fluid is withdrawn. You may feel a brief stinging sensation or a cramping/pressure feeling during this part.
• Needle Removal: The needle is then carefully removed. The baby's heart rate will be checked again via ultrasound to ensure everything is fine. A small bandage is placed on your abdomen.

After the Procedure: Recovery and Results

Immediately After

You will be asked to rest quietly for a short period before going home. You must arrange for someone to drive you.

The Next 24-48 Hours

It is essential to rest and take it easy.

• Avoid any strenuous activity, heavy lifting, or exercise.
• You may experience some mild cramping, similar to menstrual cramps, which is normal.
• You can usually return to your normal activities after a day or two, as advised by your doctor.
• Contact your doctor immediately if you experience severe cramping, heavy bleeding, leakage of clear fluid from the vagina, or a fever.

Receiving Your Results

The amniotic fluid is sent to a lab for analysis.

• Preliminary Results (FISH): A rapid test called Fluorescence In Situ Hybridization (FISH) can often provide preliminary results for the most common chromosomal abnormalities (like Down syndrome) within 24-48 hours.
• Full Karyotype Results: The complete, final results from the cell culture take longer, typically about two to three weeks.

Risks & Safety Profile

Amniocentesis is a very safe procedure when performed by an experienced specialist, but it does carry some risks that must be considered.

• Risk of Miscarriage: This is the most significant concern. Historically, the risk was quoted as high as 1 in 100. However, with modern techniques using continuous ultrasound guidance, the procedure-related risk of miscarriage is now much lower, estimated to be between 1 in 300 and 1 in 500 (approximately 0.2% to 0.3%).
• Minor Complications: Other less common risks include mild cramping, spotting or bleeding, and leakage of a small amount of amniotic fluid, all of which usually resolve on their own.
• Infection: There is a very small risk of introducing an infection into the uterus.
• Rh Sensitization: If the mother is Rh-negative and the baby is Rh-positive, there is a risk of blood mixing. This is prevented by giving an Anti-D injection.

Myths vs Facts

Take the Next Step

The decision to undergo an amniocentesis is a personal one, weighing the desire for diagnostic certainty against the small risks involved. It is a journey that should be navigated with comprehensive information and compassionate support. Our team of fetal medicine specialists and genetic counselors are here to provide you with the expert guidance you need, answering every question and ensuring you feel fully informed and supported in making the choice that is best for your family.

CTA: Book a Fetal Medicine Consultation | Get a Genetic Counselling Session

Frequently Asked Questions

1. What is the difference between an amniocentesis and a Chorionic Villus Sampling (CVS)?

Ans. Both are diagnostic tests. CVS is typically performed earlier in pregnancy (between 10-13 weeks) and involves taking a sample of tissue from the placenta. Amniocentesis is done later (15-20 weeks) and samples the amniotic fluid. Amniocentesis can also detect neural tube defects, which CVS cannot. The risk of miscarriage is similar for both procedures when performed by experienced hands.

2. How much amniotic fluid is taken? Does the baby need it?

Ans. About 20-30 ml of fluid is removed. The baby is constantly making more fluid, and this small amount is quickly replaced within a few hours.

3. Can I find out the sex of the baby from an amniocentesis?

Ans. Yes, since the test analyzes the baby's chromosomes (XX for female, XY for male), it will definitively determine the baby's sex. However, due to the PC-PNDT Act in India, the disclosure of fetal sex is illegal and will not be done.

4. What happens if I am Rh-negative?

Ans. If you have an Rh-negative blood type, you will be given an injection of Anti-D immunoglobulin after the procedure. This prevents your body from developing antibodies that could affect a future Rh-positive baby.

5. How long do I need to take off from work?

Ans. It is highly recommended to take the day of the procedure and the following day completely off to rest. You should avoid any demanding physical activity for several days.

6. What if the results show a problem?

Ans. If a diagnosis is confirmed, you will have extensive counselling with the fetal medicine specialist and a genetic counsellor. They will provide you with complete information about the condition, the prognosis, and all available options, including management of the pregnancy, planning for delivery at a specialized center, and the option of termination of pregnancy, in a supportive and non-judgmental manner.

7. Can the test results be wrong?

Ans. Amniocentesis is considered over 99% accurate for diagnosing chromosomal abnormalities. In very rare instances, there can be issues with the cell culture in the lab, which might require a repeat procedure, but this is extremely uncommon.

8. Is a local anesthetic used?

Ans. The use of a local anesthetic to numb the skin on the abdomen is an option. Some studies show it doesn't significantly change the overall sensation of pressure, while some women find it helpful. You can discuss this preference with your specialist.