SPECTROPHOTOMETRY OF AMNIOTIC-FLUID - A SIMPLE AND RAPID METHOD FOR DISTINGUISHING BETWEEN GESTATIONAL SACS IN 2ND-TRIMESTER AMNIOCENTESIS OF TWIN PREGNANCIES

Objective: To evaluate the use of an alternative and simple spectropho tometric method that could replace the intraamniotic injection of dye in the second-trimester amniocentesis of twins. Method: Optical densit ies (OD) of amniotic fluid (AF) obtained at second-trimester genetic a mniocentesis were measured at 360 nm. Comparison was made between 36 t win pregnancies and 60 singleton controls. Results: The mean differenc e in OD between two samples taken from the same sac of singleton pregn ancies was very small (mean 0.004, standard deviation [SD] 0.003). How ever, samples drawn from each of the twin pairs' amniotic sacs varied widely (raw mean 0.176, SD 0.223; median 0.096, range 0.011-0.943). Th e difference between the groups was highly significant statistically ( P < .001). Conclusion: Our preliminary experience with spectrophotomet ry of AF in twin amniocentesis suggests that this simple test may be u seful in ascertaining that the AF samples were obtained from each of t he two gestational sacs.