Randomised experimental comparison of 23G versus 22G needle for ultrasound guided invasive fetal procedures

To experimentally compare the standard 22G spinal needle with a newer 23G needle with specific ultrasound visualisation tip (Cook echotip®, Spencer, Indiana, USA) in the setting of ultrasound-guided invasive intrauterine procedures.

We first determined the size of the defects created in human fetal membranes using light microscopy and adapted area calculating software by both needles in an in vitro model performing 20 paired experiments on 4 term membrane specimens. Secondly, we determined the performance of 3 groups of operators, with different levels of experience in invasive intrauterine procedures during cordocentesis on a simulator model, using either a 22G or 23G needle. For each procedure, we measured the time required to successfully obtaining 2 ml of artificial blood in 24 paired experiments.

The mean ± SD defect sizes created was 0.66 ± 0.12 mm(2) with the 22G needle and 0.59 ± 0.13 mm(2) with the 23G needle (P = 0.11). The mean duration of sampling was 144 ± 188 sec with the 22G needle versus 140 ± 120 sec with the 23G needle (P = 0.99) for all operators pooled but four out of six operators showed shorter sampling times with a 22G needle.

This experimental study shows that the use of a 23G needle compared to a 22G needle was not associated with significantly different procedure duration or defect size.