Single-needle insertion in twin amniocentesis. 
Amniocentesis in twin gestation is an uncommon event for most medical centers.  The current technique used for this procedure includes two or more needle insertions and the introduction of dye into the first sac.  A new approach that consists of a single insertion is proposed.  The advantages of this alternate technique are that it requires only one insertion, it is a swifter procedure, it does not require the injection of dye, and it offers positive proof of tapping the two gestational sacs.  Although this technique may have some potential risks, in our judgment the advantages outweight the potential risks, and this technique should be considered and its feasibility evaluated in cases of twin gestation requiring two-sac tapping.