Efficacy of the maternal height to fundal height ratio in predicting arrest of labor disorders.

Numerous methods of identifying fetal-pelvic disproportion to its clinical presentation have been tested, but none has been consistently accurate or economically feasible. The objective of this study was to prospectively evaluate the utility of the maternal-fetal ratio (MFR) with clinical and sonographic estimates of fetal weight (FEW) for predicting active phase arrest disorders and the need for a subsequent cesarean section (C/S). Upon admission, maternal height (MH), symphyseal-fundal height (SFH), and clinical and sonographic FEW were obtained on 140 laboring women at term. The MFR was defined as MH (cm) divided by SFH (cm). A modified MFR was calculated by adjusting the SFH according to the station of the presenting part. Women delivered by C/S had a modified MFR of 3.75 +/- 0.35 compared with 4.0 +/- 0.36 for women delivering vaginally, P = 0.02. An abnormal modified MFR showed a relative risk of 7.3 (95% CI = 1.45-33.2) for predicting a C/S, while a sonographic EFW > 4,000 g had a relative risk of 3.8. The MFR of women delivered by C/S due to arrest disorders is significantly lower than that measured for women delivering vaginally. Women with an abnormal modified MFR have a sevenfold increased likelihood of having an arrest disorder. The modified MFR (which can be measured antenatally) is superior to the birth weight (which can be approximated by sonography) in predicting arrest disorders.