Uterine contraction pressures in women undergoing a trial of labor after prior cesarean delivery

Abstract

A TRIAL OF LABOR AFTER PRIOR CESAREAN DELIVERY LINDA FONSECA, SUSAN RAMIN, MICHAEL LUCAS, ALFRED SOSA, MARYCLARE DAY, LARRY GILSTRAP III, University of Texas Health Science Center at Houston, Obstetrics, Gynecology and Reproductive Sciences, Houston, TX OBJECTIVE: To evaluate the maximum uterine contraction pressures or Montevideo units (MVUs) in womenundergoing a trial of labor (TOL) after one prior cesarean. STUDY DESIGN:TheMVUs were determined during the first stage of labor for women undergoing a TOL after one prior cesarean delivery. All women included in this study were at term, had intrauterine pressure catheters (IUPCs), and were undergoing TOL during their second pregnancy. For analysis of MVUs, patients were divided into two groups. Group A included those women who had a successful TOL. Group B included those women who required repeat cesarean delivery. MVUs were also determined according to the type of labor (spontaneous, induced, or augmented). RESULTS: The mean MVU ( ± SD) for group A (n = 98) was 217 ± 79 versus 214 ± 78 for groupB (n = 45) (P = NS). 72 (73.5%) of the 98 womenwho had successful TOL (group A) achieved$200 MVUs, compared to 27 (60%) of the 45 women who had a failed TOL (group B; P = NS). The MVUs achieved in both group A and group B were similar regardless of whether labor was spontaneous (202 ± 90 [n = 55] vs 202 ± 80 [n = 13]) or if oxytocin was required (234 ± 74 [n = 43] vs 219 ± 74 [n = 32], P = NS) for either induction or augmentation. Not surprisingly, the mean birth weight for babies in group B was significantly greater than for group A (3630 ± 460 vs 3410 ± 498, P = 0.015). The mean gestational age was similar for both groups (39.5 weeks vs 40.0 weeks). CONCLUSION: Themajority of women undergoing a TOL in their second pregnancy achieved $200 MVUs regardless of whether they had a successful vaginal birth or required a repeat cesarean delivery. The number of Montevideo units achieved was not predictive of success or failure of the TOL. Women requiring repeat cesarean delivery had larger babies.