A new predictor of cephalopelvic disproportion?

Cephalopelvic disproportion (CPD) is a recognised obstetric problem with potential risk to both mother and infant. Identification of those mothers at risk of CPD is difficult and has concentrated in the past on such measurements as maternal shoe size and height. Our objective in this study was to examine new anthropomorphic parameters as indicators of CPD. This was a case controlled study of sixty consecutive women, and their partners, who had caesarean section performed for CPD and 60 case matched controls. Measurements included maternal and paternal head circumference, height, shoe-size, body mass index (BMI), infant weight and head circumference. Parity, gestation at delivery, and mode of onset of labour were recorded. Data were analysed using Stata Release 6. Prognostic factors were tested for association with CPD using conditional logic regression. The most important anthropomorphic risk factors for CPD were maternal head circumference in relation of height (P < 0.001), and paternal head to height ratio (P = 0.017). Head to height ratio is taken as the head circumference in centimeters divided by the height in metres. Body mass index was higher in CPD cases (maternal case mean = 27.1, control mean = 25.5; paternal case mean = 27.2, control mean = 26.2). Infant head circumference was not a predictor. Primiparity was an important independent predictor (P<0.001), regardless of the mode of onset of labour. Maternal or paternal shoe-size, induction of labour and gestation at delivery were not predictors. The risk profile for CPD which emerges is one of a tall father where both mother and father have large head-to-height ratios.