Amniocentesis is performed most of the time by two
operators. There are several technique options and at
least three hands are needed: one for the ultrasound
probe, one for the needle, and one to two for the syringe
to withdraw amniotic fluid. Most of the time, the main
operator holds the probe and the needle in each hand.
The assistant adapts the syringe and withdraws the fluid
Other options are favored by some teams, with the
assistant performing the ultrasound and the main
operator performing the rest of the procedure. When
the main operator holds the ultrasound probe and the
needle, he/she will unconsciously localize the ultrasound
image plane and the needle in space, since the needle is
not on the screen at the beginning of the procedure, and
continuously adapt using a 3D representation while only visualizing a 2D image. It requires skills, acquired
through learning and continuous experience.
Positioning of the needle and ultrasound probe has been
well described in 1995 by Ville et al.  and is schematized
in Fig. 1. One of the important points of this description is
positioning the target in the middle of the ultrasound
screen while trying to maintain the probe vertical. If the
target is well positioned in the middle of the screen, a
needle 20 G is inserted laterally to the probe, 3 cm away in the
same plane, at an angle of 45 ο , should arrive at the target.
Being in control of the needle also means visualizing
the entire needle on the ultrasound screen throughout
the procedure. A partial visualization can mean that the
operator does not know where the tip of the needle is.
Amniocentesis can be performed through the placenta for
technical impossibilities to do otherwise.
Figure 1 Technique for amniocentesis according to Ville et al.
Positioning for amniocentesis: the target should be positioned in the
middle of the screen, the needle inserted laterally to the probe, 3 cm
away in the same plane, at an angle of 45o
. Modified from .2 Ville Y, Cooper M, Revel A, et al. Development of a training model for Uultrasound-guided invasive procedures in fetal medicine. Ultrasound Obstet Gynecol 1995; 5:180–183.
Prenat Diagn. 2009 Jun;29(6):606-12. doi: 10.1002/pd.2256.
Antibiotic prophylaxis before second-trimester genetic amniocentesis (APGA): a single-centre open randomised controlled trial. Giorlandino C,
Oral azithromycin, 500 mg per day, was administered 3 days before amniocentesis.
Antibiotic prophylaxis before second-trimester amniocentesis reduced the risk of abortion and of rupture of the membranes.