Interpregnancy interval in multiparas: does it impact the labor curve?

Abstract

Both short and long interpregnancy intervals (IPI) are associated with adverse outcomes, however the impact of IPI on labor progression is unknown. We examined the impact of IPI on the labor curve, hypothesizing that those with a longer IPI would have a slower labor progression. This is a retrospective cohort study of multiparous patients with a history of one prior vaginal delivery admitted for induction of labor or spontaneous labor with a singleton gestation ≥37 weeks at a single academic medical center between 2004 and 2015. Repeated measures regression was used to construct labor curves which were compared between patients with a short IPI, defined as < 3 years since last delivery, and long IPI, defined as ≥3 years since last delivery. We chose this interval as it closely approximates the median birth interval in the USA. Interval-censored regression was used to estimate median duration of labor after 4-cm dilation stratified by type of labor (spontaneous versus induced). Multivariate analysis was used to adjust for potential confounders. Of the 1331 patients who were included in the analysis, 544 (41%) had a long IPI. Among the entire cohort, there were no significant differences in first stage progression between short and long IPI groups. The second stage was significantly shorter in patients with long IPI compared to those with short IPI (Table). In the stratified analysis, first stage progression varied between labor type. Long IPI was associated with a slower active phase among those being induced and quicker active phase among those in spontaneous labor (Figure). Second stage duration remained significantly shorter in the long IPI group regardless of labor type. The effect of IPI on first stage progression varies based on induction versus spontaneous labor. Regardless, a long IPI is consistently associated with a shorter second stage of labor, potentially secondary to improved physical fitness or muscle recovery with a longer IPI.View Large Image Figure ViewerDownload Hi-res image Download (PPT)