Correlation between pathology findings and ultrasonic prediction in twin pregnancy

The macroscopic and microscopic pathology fIndings in 32 twin pregnancies were compared with the antenatal sonographic classification into monochorionic and dichorionic pregnancy. The latter was based on the thickness of the intervening septum. The ultrasound diagnosis was confirmed in 24 of 30 cases giving an accuracy of 80%. Thirteen of the 24 cases were dichorionlc diamniotic type while 10 showed monochorionic d1amn1ot1c placentation. Only one case of monochorionic monoamniotic twin pregnancy was found. In six of the remaining 8 cases there was discrepancy between the ultrasound prediction and pathology findings. Definite conclusions about the chorion type could not be drawn from either ultrasound or pathology examination 1n the remaining 2 cases. No monoamniotic twin pregnancy was missed in the latter 8 cases. This is important because of the associated high mortality. The detection of monochorIonic diamniotic placentatlon is also crucial because of the unique occurrence of vascular anastomoses between the two foetal circulations and potential of developing twin-to-twin transfusion and discordancy of foetal growth. Determination of chorion type also helps in the analysis of zygosity of the twin-pregnancy and bears implication 1n genetic amniocentesis.