Monitoring contractions in obese parturients: electrohysterography compared with traditional monitoring.

OBJECTIVE: To compare electrohysterogram-derived contractions with both tocodynamometry and intrauterine pressure monitoring in obese laboring women.
METHODS: From a large database of laboring patients with electrohysterogram monitoring, obese subjects were selected in whom data were recorded for at least 30 minutes before and after intrauterine pressure catheter placement for obstetric indication. Using a contraction detection algorithm, the relationship between the methods was determined with regard to both frequency and contraction duration.
RESULTS: Of the 25 subjects (median body mass index 39.6 [25th percentile 36.5, 75th percentile 46.3]), seven underwent amniotomy at the time of intrauterine pressure catheter placement. Tocodynamometry identified 248 contractions compared with 336 by electrohysterography, whereas intrauterine pressure catheter monitoring identified 319 contractions compared with 342 by electrohysterography. Using the Contractions Consistency Index, electrohysterogram contraction detection correlated better with the intrauterine pressure catheter (0.94+/-0.06) than with tocodynamometry (0.77+/-0.25), P=.004. Electrohysterogram-derived contraction lengths closely approximated those calculated from the intrauterine pressure catheter signal.
CONCLUSION: Contraction monitoring routinely is employed for managing labor, and tocodynamometry may be unreliable in obese parturients. In the obese women in this study, the electrohysterogram-derived contraction pattern correlated better with the intrauterine pressure catheter than tocodynamometry. Electrohysterography may provide another noninvasive means of monitoring labor, particularly for those women in whom tocodynamometry is inadequate.