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Published on: September 5, 2011
Chorionicity determination in twin pregnancies: how accurate are we?
E Stenhouse1, C Hardwick, S Maharaj
1Department of Obstetrics and Gynaecology, Glasgow Royal Maternity Hospital, Glasgow, UK.
Objectives:
To determine the accuracy of antenatal prediction of chorionicity in twin pregnancies in our institution.
Methods:
Antenatal chorionicity was determined using the number of placental masses, the presence or absence of a twin peak sign and the fetal sex. The gestational age at assessment was documented. Postnatal diagnosis of chorionicity was determined by neonatal sex and placental pathology.
Results:
Chorionicity was correctly determined in 95% of cases (n = 131); 91% of the monochorionic and 96% of the dichorionic pregnancies were correctly determined. If chorionicity was assessed prior to 14 weeks' gestation (n = 96) the correct diagnosis was made in all except one case.
Conclusions:
Ultrasound assessment of chorionicity has a high sensitivity and specificity. This is further improved if the assessment is performed prior to 14 weeks' gestation.
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