Objective: Our aim was to determine the chorionic and amniotic types in multifetal pregnancies with transvaginal ultrasonography at > or = 14 weeks' gestation.
Study design: Two hundred twelve multifetal pregnancies were scanned transvaginally at or before 14 weeks' gestation. The number of fetuses and the chorionic and amniotic type were determined ultrasonographically. Of the 212 patients, 54 were delivered at our institution, and 43 of these 54 had pathologic evaluation of the placenta. Ultrasonographic and pathologic correlation of the chorionic and amniotic type was assessed in this group.
Results: Ultrasonographic evaluation of the 212 pregnancies demonstrated 64 twin, 87 triplet, 41 quadruplet, 18 quintuplet, 1 sextuplet, and 1 septuplet gestation. Nine of the twin pregnancies were monochorionic-diamniotic; two of the triplets were dichorionic-triamniotic, and four of the quadruplets were trichorionic-quadraamniotic. In the 43 patients with both ultrasonographic and pathologic assessment, there were 40 twins, five of which were monochoronic diamniotic type. All three triplets were trichorionic-triamniotic type. In all 43 transvaginal ultrasonography correctly predicted the chorionic and amniotic type as determined by the pathologic findings.
Conclusions: Transvaginal ultrasonography at < or = 14 weeks can easily and accurately determine the chorionic and amniotic type in multifetal pregnancies.