Pure fetal blood from the umbilical cord obtained at fetoscopy: experience with 125 consecutive cases.

With experience, and with the use of a 30-degree forward-oblique viewing telescope, sampling from one of the vessels of the umbilical cord produced at least 0.5 ml of pure fetal blood in 97% of the cases between 14 and 24 weeks' gestation; by aspiration through a short-tipped, 27-gauge, specially constructed needle, adequate samples were ensured. The technique used overcomes the problems previously encountered with sampling from an anteriorly situated placenta, and offers considerable potential for investigating intrauterine physiologic and pharmacologic features, as well as providing excellent specimens for diagnostic purposes. With this method, the calculated optimum time for fetoscopy and sampling of fetal blood is 16 to 18 weeks' gestation.