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Poster session I Clinical obstetrics, epidemiology, fetus, medical-surgical complications, neonatalogy, physiology/endocrinology, prematurity: Abstracts 87 - 236| Volume 208, ISSUE 1, SUPPLEMENT , S61-S62, January 01, 2013

114: A proportion score of pelvic and neonatal head circumference is highly predictive of instrumental delivery and cesarean section due to cephalo-pelvic disproportion

      Objective

      To evaluate the risk for instrumental delivery (ID) and cesarean section due to cephalo-pelvic disproportion (CS-CPD), according to maternal pelvic CT parameters, and neonate weight and head circumference.

      Study Design

      We studied patients who delivered at term a singleton fetus in vertex presentation, and had underwent an abdominal CT in our institution. Pelvimetry was performed retrospectively. We analyzed the relation between maternal pelvic parameters, neonatal weight and head circumference (HC), and the mode of delivery.

      Results

      We enrolled 111 cases: 84 patients had NVD, 7 had ID and 20 had CS-CPD. The neonatal HC was significantly larger in ID and CS-CPD in comparison to NVD (34.9±1.1, 34.9±2.5 and 33.8±1.7 cm, respectively, p=0.03). The transverse diameter of the mid pelvis was significantly smaller in ID and CS-CPD in comparison to NVD (9.5±1.1, 9.8±0.9 and 10.4±0.8 cm respectively, p=0.002). We expressed the composed A-P and lateral parameters of the pelvic inlet, mid and outlet, with a “naive formula” of estimated ellipse circumference (EEC). The mid pelvic EEC was significantly smaller in ID and CS-CPD in comparison to NVD (32±2.6, 33.5±3.5 and 34.8±2.3 cm respectively, p=0.034). We used the ratio between the pelvic EEC and HC to express a proportion score (PS) for CPD. The PS was significantly smaller in ID and CS-CPD, in comparison to NVD, in all pelvic levels: inlet (1.08±0.1 and 1.09±0.1 VS 1.15±0.08, p=0.006); mid (0.92±0.09 and 0.97±0.1 VS 1.03±0.08, p=0.0003); and outlet (0.77±0.04 and 0.81±0.07 VS 0.84±0.08 p=0.011). ROC analysis showed that a mid pelvis PS of 1 had a 68% sensitivity, 58% specificity and a positive predictive value of 89% for CS-CPD.

      Conclusion

      Low proportion score of maternal pelvic parameters and neonate head circumference, is highly correlated with ID and CS-CPD.