Validity of intrauterine pressure measurements with transcervical intra-amniotic catheters and an intra-amniotic miniature pressure transducer during labor.

The accuracy of transvaginal intrauterine pressure measurements was determined in 21 subjects in labor, 12 of which were monitored with two transcervical intrauterine catheters and one miniature intrauterine pressure transducer, and 9 subjects of which were monitored with a double lumen transcervical catheter. Statistical analysis of variance of data from the first group showed significant sensor variations. Pressure amplitude ratios between different sensors for the same contraction were calculated for all contractions and were found to vary with a coefficient of variation of greater than 23%. This value was reduced to less than one half when a double lumen catheter with adjacent tips was used or only smooth bell-shaped contractions were considered. The internal transducer was shown to give equivalent data to that obtained from the catheter and external pressure transducer combinations. It is concluded that no single uterine pressure observation is an accurate reflection of uterine pressure during labor.