The effect of tocolytics in women with preterm labor after 34 weeks of gestation: A propensity score-matched study

Abstract

Objectives: Since late preterm neonates are physiologically less mature than term neonates, the use of antenatal corticosteroids in the late preterm period has been recommended. The use of tocolytics can also be considered to gain valuable time for using antenatal corticosteroids in the late preterm period. In this study, we examined the efficacy of tocolytics on prolonging pregnancy in the late preterm period, by comparing women who received tocolytics with those who received none.

Study design: This retrospective cohort study included women who were admitted due to preterm labor after 34 weeks of gestation and delivered in the late preterm period. Primary outcome was time from admission to delivery (days). Secondary outcomes were the proportion of preterm births within 2 days, and within 7 days, completed cycles of antenatal corticosteroids, and the neonatal outcomes. Primary and secondary outcomes were compared according to the use of tocolytics. Propensity score matching was performed to create comparable groups. The maternal age, pre-pregnancy body mass index, nulliparity, history of preterm birth, hypertensive disease during pregnancy, gestational diabetes mellitus, history of preterm labor, gestational age at admission, cervical length, and the number of contractions were the baseline characteristics included in the propensity score.

Results: Of 275 women, 44 women received tocolytics (tocolytics group) and 231 women did not (no tocolytics group). We matched 44 women who received tocolytics and 44 women who didn't. The tocolytics group was shown to exhibit a longer time from admission to delivery than the no tocolytics group, with a hazard ratio for tocolytics of 0.4 (95 % confidence interval, 0.2-0.6). In addition, the proportion of preterm births occurring within 2 days and 7 days were lower in those receiving tocolytics compared to those that didn't.

Conclusion: In this propensity score matched-study, the use of tocolytics had a significant effect on pregnancy prolongation, which allows more time for use of corticosteroids in women with preterm labor after 34 weeks of gestation.

Keywords: Obstetric labor; Premature; Premature birth; Propensity score; Tocolytic agents.