Departments of Obstetrics and Gynecology, Stanford University, Stanford, California, the University of Texas Southwestern Medical Center, Dallas, Texas, the University of Alabama at Birmingham, Birmingham, Alabama, the University of Utah Health Sciences Center, Salt Lake City, Utah, the University of Texas Health Science Center at Houston–Children's Memorial Hermann Hospital, Houston, Texas, the University of Pittsburgh, Pittsburgh, Pennsylvania, Northwestern University, Chicago, Illinois, Wayne State University, Detroit, Michigan, Drexel University, Philadelphia, Pennsylvania, Brown University, Providence, Rhode Island, MetroHealth Medical Center, Case Western Reserve University, Cleveland, Ohio, the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, Columbia University, New York, New York, and The Ohio State University, Columbus, Ohio; the George Washington University Biostatistics Center, Washington, DC; and the Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland.
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OBJECTIVE:To assess the association of cervical effacement with the rate of intrapartum cervical change among nulliparous women.METHODS:We conducted a secondary analysis of a prospective trial of intrapartum fetal pulse oximetry. For women who had vaginal deliveries, interval-censored regression was used to estimate the time to dilate at 1-cm intervals. For each given centimeter of progressive cervical dilation, women were divided into those who had achieved 100% cervical effacement and those who had not. The analysis was performed separately for women in spontaneous labor and those who were given oxytocin.RESULTS:A total of 3,902 women were included in this analysis, 1,466 (38%) who underwent labor induction, 1,948 (50%) who underwent labor augmentation (combined for the analysis), and 488 (13%) who labored spontaneously. For women in spontaneous labor, the time to dilate 1 cm was shorter for those who were 100% effaced starting at 4 cm of cervical dilation (P=.01 to <.001). For women who received oxytocin, the time to dilate 1 cm was shorter for those who were 100% effaced throughout labor (P<.001).CONCLUSION:The rate of cervical dilation among nulliparous women is associated with not only the degree of cervical dilation, but also with cervical effacement.CLINICAL TRIAL REGISTRATION:ClinicalTrials.gov, www.clinicaltrials.gov, NCT00098709.