Amniocentesis is an invasive procedure that requires removing the amniotic fluid to obtain fetal cells for chromosomal analysis. The procedure is usually performed between 15-18 weeks gestation and is done under ultrasound guidance.
Why it’s Done
Amniocentesis is most commonly done to diagnose the fetal chromosomal anomalies, after detecting fetal structural abnormalities on ultrasound that could be markers for chromosomal abnormalities, those with a previously affected child or with a family history of a genetic disorder, women over 35 and those with a serum screening positive for Down syndrome or trisomy 18. It can also be done to test fetal lung maturity, fetal infections and to evaluate the severity of fetal anaemia in cases of Rh sensitization.
Therapeutic uses for an amniocentesis may include the direct delivery of medications to the unborn fetus and to release intrauterine pressure in the presence of polyhydramnios.
How You Prepare
Ideally, amniocentesis is performed at 15-18 weeks of pregnancy to give the patient the choice of termination of pregnancy if any chromosomal abnormalities are detected. The patient is explained about the procedure and the consent is obtained. An ultrasound will be performed to check the fetal heart rate, the position of the placenta, fetus, and umbilical cord, and to locate a pocket of amniotic fluid. Amniocentesis is done under ultrasound guidance and the operator passes a needle through your abdomen, into the uterus and the amniotic sac. A small amount of amniotic fluid is withdrawn into a syringe. The amount depends upon the type of testing that will be performed. The fluid will be placed into a special light-protected container and the needle will be removed.
What you can expect
Notify your doctor if you have:
- Bleeding or leaking of amniotic fluid from the needle puncture site or the vagina
- Severe abdominal pain/Cramps during or after the procedure
You should rest at home and avoid strenuous activities for at least 24 hours and a ultrasound is repeated after 3 days for reassurance.
Results/ Post Procedure
The mother and the fetus will be monitored after the procedure. The fetus heart rate and your vital signs will be reassessed. You should rest at home and avoid strenuous activities for at least 24 hours and a ultrasound is repeated after 3 days for reassurance. Amniotic fluid will be sent to specialty genetic lab for analysis and depending on test results, counseling with a genetics specialist may be recommended.
What Are the Risks?
Miscarriage is the most common risk post amniocentesis. The risk also depends on the gestational age at the time of the procedure. Amniocentesis before 14 weeks has an increased risk for pregnancy loss and increased limb disruption defects. The risk of miscarriage is 0.6% if it is done at 15-18weeks. The other risks include leaking of the amniotic fluid either from the procedure site/vagina, bleeding, preterm labour, uterine infection.