[Reliability of sonographic diagnosis of chorionicity and amnionicity in twin pregnancy ].

OBJECTIVES

The aim of the study was to compare the reliability of chorionicity determination in twin pregnancy using different ultrasonographic methods as compared with post-partum placental assessment.

STUDY

DESIGN

The study included 262 spontaneous twin pregnancies delivered at Kutno Hospital between 1989 and 1996. All twin gestations were diagnosed by sonography by the 28-th week's gestation. The ultrasonographic and pathologic correlation between the chorionic and amniotic type was assessed in this group.

RESULTS

The ultrasonographic evaluation of the 262 spontaneous twin gestations demonstrated 181 (69.1%) dichorionic and 81 (30.9%) monochorionic twin pregnancies. Three of monochorionic twins were monoamniotic. In all 262 transvaginal and abdominal ultrasonography correctly predicted the chorionic and amniotic type as determined by the pathologic findings.

CONCLUSIONS

Ultrasonography before the 28-th week can accurately determine the chorionic and amniotic type in twin pregnancies. The determination of chorionicity during the first half of pregnancy should be based on the various signs. In the second half of pregnancy, the obstetrician should rely on fetal sex in combination with the number of placentas, and characteristics of the dividing membrane.