A 29-gauge atraumatic needle for amniocentesis.

OBJECTIVE: To compare perforation characteristics of standard 22 G (0.7 mm) to 29 G needle (0.34 mm) for amniocentesis.

METHODS: Seventeen human chorio-amnion membranes were perforated immediately after cesarean section using 22 G needle for spinal anesthesia and 29 G "pencil-point" needles for amniocentesis under in-vitro conditions. Area of perforation was determined using a microscope and volume of fluid leakage was measured over a period of 5 min.

RESULTS: Membrane perforation with the 22 G needle resulted in a mean damaged area of 225,147.4 μm(2), a hole with a mean area of 50,154 μm(2) and amniotic fluid volume passage of 17.5 mL/5 min, whereas the 29 G needle generated a mean damaged area of 114,812.4 μm(2), a hole with an average area of 1382.5 μm(2) and volume passage of 0.28 mL/5 min. These differences were significant.

CONCLUSION: The hole formed by membrane perforation with 29 G "pencil-point" needle for amniocentesis is 36 times smaller, and the amniotic fluid loss is 61 times less than that measured with the 22 G standard needle for spinal anesthesia. Significant reduction of complications following amniocentesis is expected with the 29 G needle.