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, G 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).