Can third trimester ultrasound predict the presentation of the first twin at delivery?

OBJECTIVE

To determine the ability of early sonogram to predict the presentation of twin A at birth.

METHODS

A retrospective cohort study was conducted on all twin pregnancies evaluated at our Fetal Evaluation Unit from 2007 to 2009. Sonogram records were reviewed for the presentation of twin A at seven gestational age intervals and inpatient medical records were reviewed for the presentation of twin A at delivery. The positive predictive value, sensitivity, and specificity of presentation as determined by ultrasound, at each gestational age interval, for the same presentation at delivery were calculated.

RESULTS

Two hundred and thirty-eight twin pregnancies met inclusion criteria. A total of 896 ultrasounds were reviewed. The positive predictive value of cephalic presentation of twin A as determined by ultrasound for the persistence of cephalic presentation at delivery reached 95% after 28 weeks gestation. The positive predictive value for noncephalic presentation as established by sonogram for noncephalic at delivery was >90% after 32 weeks gestation.

CONCLUSIONS

The presentation of the first twin at delivery can be determined by sonogram by the 32nd week of gestation in over 90% of twin pregnancies.