Amniocentesis, a needle aspiration of amniotic fluid for laboratory analysis, is usually performed between 14 and 20 weeks' gestation. This procedure can detect chromosomal and neural tube defects, metabolic and other disorders, and the sex of the fetus. It also helps assess overall fetal health. When performed in the final trimester, amniocentesis helps to evaluate fetal lung maturity and detect Rh hemolytic disease.
Amniocentesis is indicated when maternal age is over 35 and in patients with a family history of chromosomal or neural tube defects or inborn errors of metabolism. Another test, chorionic villi sampling, can also be used to detect fetal disorders.
Amniocentesis is contraindicated when the anterior uterine wall is completely covered by the placenta or when amniotic fluid is insufficient.
Hospital gown 
two sets of sterile gloves, sterile gowns, and masks stethoscope Doppler stethoscope and other appropriate ultrasound equipment or electronic fetal monitor antiseptic solution with sterile container local anesthetic alcohol 10-mL syringe sterile 20G or 22G 4'' spinal needle with stylet 22G or 25G needle sterile 20-mL glass syringe clean amber glass specimen container for Rh sensitization and lecithin-sphingomyelin (L/S) ratio tests three sterile glass specimen tubes (for genetic tests) laboratory request forms adhesive bandage.
Preassembled amniocentesis trays are available.
If you don't have an amber specimen container, cover the outside of a clean test tube or glass container with adhesive tape or aluminum foil to prevent the breakdown of bilirubin. Properly label all specimen containers or tubes.
- Identify the patient using two patient identifiers per the facility policy.
- Make sure that the consent form is signed.
- To reduce the risk of bladder puncture, ensure that the patient voids before the procedure if the pregnancy exceeds 20 weeks (before 20 weeks, a full bladder may help to hold the uterus steady).
Hip helper
- Provide privacy and explain the procedure to the patient. Have the patient put on a hospital gown and assist him to a supine position. Obtain baseline maternal vital signs. Next, determine the baseline FHR with a Doppler handheld device, Doppler stethoscope, or the fetoscope.
- Instruct the patient to fold her hands on her chest or rest her hands behind her head and tell her to remain still. Provide reassurance to the patient.
- The doctor will use ultrasonography to locate the fetus, placenta, and amniotic fluid pocket to determine the appropriate needle-insertion depth. Next, he'll put on the sterile gown, sterile gloves, and mask and clean the skin with an antiseptic solution.
Pain relief prep
- If the patient is receiving a local anesthetic, clean the diaphragm of the multidose vial of anesthetic solution with alcohol. Provide a 10-mL syringe and a 22G or 25G needle. Then invert the bottle to allow the doctor to withdraw the anesthetic.
Scrub in
- Perform hand hygiene and put on a sterile gown, sterile gloves, and mask.
- After the anesthetic takes effect, the doctor, guided by ultrasonographic imaging, advances the 20G needle with a stylet through the abdomen and uterine wall into the amniotic sac, removes the stylet, attaches the 20-mL glass syringe to the needle, and aspirates the amniotic fluid.
What's the order?
- If the patient is having genetic studies, open the sterile glass specimen tubes for the physician to transfer the amniotic fluid, then promptly close the tubes avoiding contamination.
- If the patient is having Rh sensitization or L/S ratio tests, open the amber or covered specimen container for the amniotic fluid and close the container promptly.
- After the needle is withdrawn, place an adhesive bandage over the insertion site.
Let's go to the lab
- Label the specimens and verify the information from the medical record matches the labels and the requisition. Send the specimens to the laboratory immediately.
- If the patient is in the final trimester of pregnancy, direct her to lie on her side.
Irritation inspection
- Assess maternal vital signs and FHR every 15 minutes for 30 minutes for tachycardia or bradycardia. Notify the doctor and continue to monitor FHR if these signs appear. In addition, electronically monitor the patient for uterine irritability and the fetus for changes in heart rate pattern for a few hours after the procedure.
- Instruct the patient to report signs and symptoms of complications, including a vaginal discharge (fluid or blood), decreased fetal movement, contractions, or fever and chills. (See Complications of amniocentesis.)
- Help the patient dress in preparation for discharge.
- Inform the patient, her family, and her support person, as appropriate, that test results should be available in 2 to 4 weeks. Provide emotional support as needed. (See Documenting amniocentesis.)
Outline