Intrauterine pressure: comparison of extra vs intra amniotic methods using a transducer tipped catheter

Fourteen women admitted in early labor, with intact membranes, were studied. In each woman, two catheters were inserted transcervically; one catheter was inserted into the extraamniotic space before rupture of membranes, and the second catheter was inserted, after artificial rupture of membranes into the intraamniotic cavity. The contraction to contraction difference in active pressure (pressure above the baseline) recorded by the two catheters, as well as the cumulative total active pressure generated (calculated by adding the active pressure of all contractions) throughout labor by the two catheters were compared. Of the 606 contractions analysed, 43.2% showed pressure difference of 0-5 mmHg between the intra amniotic and extraamniotic catheter; 21.3% showed 6-10 mmHg difference, 12.2% showed a difference of 11-15 mmHg, and 23.3% showed a difference greater than 15 mmHg. When total active pressure generated by each catheter for individual patients was calculated, the percentage difference varied from 2.3% to 53.7%. Intrauterine pressure measurements in labour using transducer-tipped catheters inserted in the extraamniotic space may not provide comparable information to a similar catheter inserted intraamniotically when membranes are ruptured.