(489) Prediction of Cesarean Delivery Using Maternal Measurements – Secondary Analysis of a Prospective Multicenter Study

Prediction of intrapartum cesarean delivery (CD) would be of significant benefit in reducing labor-associated morbidity. While different fetal sonographic biometric parameters have been studied to develop individual patient CD risks, they are subject to ultrasound resource limitations, as well as interobserver variability in ultrasound precision. Our objective was to evaluate whether simple, easily repeatable measurements of a pregnant woman’s head circumference and her height could provide an easy method of CD risk prediction in routine antenatal clinics.


Study Design: A multi-center prospective study recruited 2,336 nulliparous women with a vertex presentation between 39+0 and 40+6 weeks’ gestation at seven hospitals to examine a range of CD predictors. Maternal head circumference (MHC) and maternal height (MH) were recorded at the first antenatal visit, with data entered into a prospective database at study enrolment at 39+0 to 40+6  weeks’ gestation. Maternal proportionality of MHC to MH was assessed using the ratio MHC:MH.

Results: From a total enrolled cohort of 2,336 nulliparous patients, 491 (21%) had an unplanned CD. Mean MHC was 56.2cm (SD=1.8cm, range=50.0-65.5cm). Mean MH was 165.5cm (SD=6.3cm, range=142-188cm). The mean MHC:MH ratio was 0.346 (SD=0.015), and this was used to standardize the MHC:MH ratio (sMHC:MH) for risk calculation. Table 1 shows that the sMHC:MH ratio was more predictive of emergency intrapartum CD than any maternal or fetal measurement individually (OR=1.65, 95%CI 1.49-1.83, p< 0.001, AUC=0.64). Table 2 shows delivery outcomes based on quartile of sMHC:MH.

Conclusion: We have demonstrated that a simple ratio of MHC to MH is a useful predictor of CD, showing that the shortest patients with the largest maternal head measurements have a 1 in 3 chance of requiring CD, with CD at full dilation and failure to progress being significantly more likely. In particular when late pregnancy ultrasound resources may be limited, a simple maternal biometry ratio can be a powerful predictor of emergency intrapartum CD, at no cost.