Effect of calcium channel blocker on labor curve in pregnant individuals with chronic hypertension.

OBJECTIVE: To compare the labor progress between individuals who received calcium channel blocker (CCB) and those who did not receive CCB during labor.

METHODS: This was a secondary analysis of a retrospective cohort study of individuals with chronic hypertension who underwent vaginal delivery at a tertiary care center from January 2010 to December 2020. We excluded individuals with prior uterine surgeries, and a 5-minute Apgar score of less than 5. We used a repeated-measures regression with a 3rd order polynomial function to compare the average labor curves according to antihypertensive medication. Estimates of the median (5th-95th percentile) traverse times between two dilations were computed using interval-censored regression.

RESULTS: Of 285 individuals with chronic hypertension, 88 (30.9%) received CCB. Individuals who received CCB during labor compared to those who did not were more likely to deliver at earlier gestational age and to have pregestational diabetes and superimposed preeclampsia (P < 0.01). The progress of labor in the latent phase was not found to be significantly different between both groups (median 11.51 hours vs. 8.74 hours; P = 0.08). However, after stratification by parity, nulliparous individuals who received CCB during labor were more likely to have a longer latent phase of labor (median 14.4 hours vs. 8.5 hours; P = 0.03) Conclusion: A calcium channel blocker may slow the latent phase of labor in individuals with chronic hypertension. Aiming to minimize intrapartum iatrogenic interventions, allowing adequate time for pregnant individuals during the latent phase of labor is especially important if individuals are on a calcium channel blocker.