IS INTERTWIN BIRTH-WEIGHT DISCORDANCE PREDICTABLE

Objective: To compare the efficacies of intertwin difference in abdomi nal circumferences (ACs) and estimated fetal weights (EFWs) to predict birth weight discordance in twin gestations. Methods: Ninety pairs of twins with sonographic measurements of AC and femur length, performed within 2 weeks before delivery, were included in the study. The EFW w as calculated (Hadlock's formula). We used Bayes' theorem and the Mant el-Haenszel chi(2) test to calculate and compare the rates of false-po sitive and false-negative prediction of the cutoff values of 15, 20, a nd 25% intertwin birth weight discordance by the intertwin EFW differe nce and an intertwin AC difference of greater than or equal to 18 mm. Results: There was no significant difference between the two methods t o predict birth weight discordance at 15-25% discordance (p = 0.254, O R = 0.33, 95% CI = 1.45-0.24) and at >25% discordance (p = 0.112, OR = 0.18, 95% CI = 0.03-1.34). Conclusions: Both the intertwin AC differe nce (greater than or equal to 18 mm) and intertwin EFW difference have similar negative predictive values and the same efficacy to exclude d iscordant growth. Because of the relatively low positive predictive va lues, birth weight discordance cannot be accurately predicted by eithe r method.