An amniocentesis is performed to obtain amniotic fluid for prenatal genetic studies, testing for fetal infections, or assessing lung maturity. The patient must sign an informed consent form at least 24 hours before the procedure. Ideal gestational age is 16 weeks or later. Ultrasound is used to visualize the fetus and guide insertion of a needle through the abdominal wall and into the amniotic sac to withdraw amniotic fluid samples.

1. How to perform an amniocentesis
Mónica Cruz-Lemini, Miguel Parra-Saavedra, Virginia
Borobio, Mar Bennasar, Anna Goncé, Josep M
Martínez, Antoni Borrell.

2. How to: perform an amniocentesis
Indications: prenatal genetic studies, fetal infection, intraamniotic
inflammation, fetal lung maturity
Sign informed consent form: ideally 24hrs before the procedure
Pre-procedure laboratories: RhD and viral (HBV, HCV and HIV)
status
Evaluate contraindications and drug adjustment
When? The ideal gestational age is ≥ 16 weeks
Machine settings: routine obstetric scan

3. Figure S1
Material requirements for performing an amniocentesis. Sterile gauze and
antiseptic, sterile sheets, sterile ultrasound probe cover, sterile gel, 20 - 22G needle,
two 10mL syringes or Vacutainer® 10mL tubes without additives (optional) and Luer
adaptor attached to Vacutainer® holder (optional).

4. Figure S2
Transverse sweep of the maternal abdomen in a sagittal view. The ultrasound
probe must be placed in a transverse plane to the maternal abdomen, always
perpendicular to the maternal skin, taking care that it does not inadvertently slide.

5. Figure S3
Puncture of the maternal abdominal wall into the uterine cavity in a
transverse view. Note the needle and the ultrasound probe at 45⁰ with regards to
the mid-sagittal plane of the maternal abdomen.

6. Figure S4
Needle introduction into the uterine cavity and “tenting” image.

7. Figure S5
Amniotic fluid aspiration with the Vacutainer® system (optional).