Optimal Admission Cervical Dilation in Spontaneously Laboring Women

Objective To estimate the impact of admission cervical dilation on the risk of cesarean in spontaneously laboring women at term. Study Design Secondary analysis of a prospective cohort study of women admitted in term labor with a singleton gestation. Women with rupture of membranes before admission, induction of labor, or prelabor cesarean were excluded. The association between cesarean and cervical dilation at admission was estimated, and results were stratified by parity. Relative risks (RRs) and 95% confidence intervals (CIs) were calculated, using cervical dilation ≥ 6 cm as the reference group. Cesarean for arrest was secondarily explored. Results A total of 2,033 spontaneously laboring women met inclusion criteria. Women admitted at <6 cm dilation had an increased risk of cesarean compared with those admitted at ≥6 cm (13.2 vs. 3.5%; RR 3.73; 95% CI 1.94-7.17). The increased risk was noted in nulliparous (16.8 vs. 7.1%; RR 2.35; 95% CI 0.90-6.13) and multiparous (11.0 vs. 2.5%; RR 4.36; 95% CI 1.80-10.52) women, but was statistically significant only in multiparous women. Conclusions Decreasing cervical dilation at admission, particularly <6 cm, is a modifiable risk factor for cesarean, especially in multiparous women. This should be considered in the decision-making process about timing of admission in term labor.