Risk of preterm delivery in women with a history of preterm labor successfully arrested by tocolytic treatment in their previous pregnancy.

Introduction: We aimed to determine if women with a history of preterm labor successfully arrested by tocolytic treatment who gave birth at term in their previous pregnancy are at an increased risk of preterm delivery in their next pregnancy.

Material and methods: This case-control study included women with two consecutive singleton pregnancies who gave birth in the 15-year period of 2000-2014 at the tertiary hospital of Poissy-Saint-Germain. Cases (preterm labor [PTL] group) included all women admitted with intact membranes for preterm labor that was successfully arrested by tocolytic treatment between 24 + 0 and 34 + 6 weeks' gestation and who gave birth at term in the first of these two pregnancies. Two control groups were selected: (i) a spontaneous preterm delivery (sPTD) group including all women with a preterm delivery in the first pregnancy, and (ii) a term delivery (TD) group that included women selected among those who gave birth at term in the previous pregnancy. The primary outcome was the spontaneous preterm birth in the next pregnancy.

Results: The PTL, sPTD, and TD groups included 114, 50, and 114 women, respectively. There were no significant differences for maternal age, body mass index, or relationship situation for both pregnancies. The mean (± SD) gestational age at the first study delivery was 39.1 (±1.2) weeks in the PTL group, 33.2 (±3.7) weeks in the PTD group, and 39.6 (±1.2) weeks in the TD group (p < 0.001 for each comparison). The delivery rate before 37 weeks of gestation in the subsequent pregnancy was 18.4% in the arrested PTL group, 34.0% in the PTB group, and 4.4% in the TD groups (p = 0.047 between arrested PTL and sPTD; p < 0,001 between arrested PTL and TD) and before 34 weeks, 6.1%, 16.0%, and 0%, respectively (p = 0.044 between arrested PTL and sPTD; p < 0,001 between arrested PTL and TD).

Conclusions: Women with a history of preterm labor that was successfully arrested by tocolytic treatment, resulting in a TD, are at a higher risk of preterm delivery in their next pregnancy than women with no such history, but a lower risk than those with a preterm delivery in their last pregnancy.