EARLY FIRST-TRIMESTER ULTRASOUND PROVIDES A WINDOW THROUGH WHICH THE CHORIONICITY OF TWINS CAN BE DIAGNOSED IN AN IN-VITRO FERTILIZATION (IVF) POPULATION

Purpose: Early and accurate diagnosis of placentation alerts the obste trician to potential clinical sequelae. The reproductive endocrinologi st has a unique opportunity to sonographically evaluate the very early intrauterine pregnancy. nancy. We undertook this study to determine w hether chorionicity could accurately be predicted using early first-tr imester transvaginal ultrasound. Results: Of 47 sets of twins conceive d through our IVF-ET program, all underwent detailed transvaginal sono graphy. These findings were then compared with results of placental pa thology examination, after birth. Transvaginal sonography was performe d 41 days following embryo transfer. All 3 monochorionic placentas wer e correctly predicted by ultrasound, while the remaining 44 placentas were dichorionic. Conclusions: The significance of our findings lies b oth in our 100% accuracy in diagnosis and in the extremely early gesta tional age at which we were able to establish correctly the diagnosis of chorionicity. The errors in diagnosis made by previous investigator s were often the result of not recognizing single placentae which were later. histologically shown to be the result of placental fusion. The infertility specialist has a unique window of opportunity to evaluate placentation and should provide useful information regarding chorioni city to the obstetrical team.