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 obstetrician to potential clinical sequelae. The reproductive endocrinologist has a unique opportunity to sonographically evaluate the very early intrauterine pregnancy. We undertook this study to determine whether chorionicity could accurately be predicted using early first-trimester transvaginal ultrasound. Results: Of 47 sets of twins conceived through our IVF-ET program, all underwent detailed transvaginal sonography. These findings were then compared with results of placental pathology examination, after birth. Transvaginal sonography was performed 41 days following embryo transfer. All 3 monochorionic placentas were correctly predicted by ultrasound, while the remaining 44 placentas were dichorionic. Conclusions: The significance of our findings lies both in our 100% accuracy in diagnosis and in the extremely early gestational age at which we were able to establish correctly the diagnosis of chorionicity. The errors in diagnosis made by previous investigators 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 chorionicity to the obstetrical team.