Background
Previous cesarean delivery is the major risk factor for uterine rupture in subsequent
trial of labor. It has been suggested that a previous preterm cesarean delivery is
associated with an increased risk of uterine rupture compared with a previous term
cesarean delivery. However, the proposed association has only been investigated in
a few studies and never in a study based on unselected contemporary prospectively
collected data.
Objective
This study aimed to investigate the risk of uterine rupture among women attempting
trial of labor after 1 previous preterm cesarean delivery compared with women with
1 previous term cesarean delivery.
Study Design
In this population-based cohort study, we used the Swedish Medical Birth Register
between 1983 and 2016 and identified 9300 women with 1 previous preterm index cesarean
delivery, 57,168 women with 1 previous term index cesarean delivery, and a second
outcome delivery defined as trial of labor after 1 previous cesarean delivery. The
risk of the main outcome uterine rupture and secondary outcomes placental abruption;
placenta accreta spectrum; postpartum hemorrhage; blood transfusion; appearance, pulse,
grimace, activity, and respiration of <7 at 5 minutes; neonatal cerebral dysfunction;
and neonatal seizures were assessed using multivariate logistic regression models
adjusted for potential confounders.
Results
Among women with a preterm index cesarean delivery, 102 (1.1%) had uterine rupture
in the outcome delivery compared with 759 of women (1.4%) with term index cesarean
delivery. This corresponded to a decreased risk of uterine rupture for women with
preterm index cesarean delivery (odds ratio, 0.79; 95% confidence interval, 0.64–0.97),
which did not remain significant in the analysis adjusted for maternal age, interdelivery
interval, maternal body mass index, maternal height, induction of labor, postoperative
infection after index cesarean delivery, and birthweight (odds ratio, 0.94; 95% confidence
interval, 0.74–1.18). Stratifying by gestational week at index cesarean delivery (32+0
to 36+6 and <32+0 weeks’ gestation) did not alter the main result. Stratifying by
interdelivery interval revealed that women with a preterm index cesarean delivery
were at a decreased risk of uterine rupture (odds ratio, 0.55 [95% confidence interval,
0.39–0.78]; adjusted odds ratio, 0.74 [95% confidence interval, 0.51–1.07]) in interdelivery
intervals of >36 months whereas there were no significant differences within other
time intervals. Of the secondary outcomes, 89 women (1.0%) with preterm index cesarean
delivery were diagnosed as having placental abruption compared with 331 women (0.6%)
with term index cesarean delivery, which corresponded to an approximately 60% increased
risk (odds ratio, 1.66; 95% confidence interval, 1.31–2.10), which remained significant
after adjusting for confounders (odds ratio, 1.49; 95% confidence interval, 1.13–1.96).
Likewise, there was a slightly increased risk of postpartum hemorrhage for women with
preterm index cesarean delivery (adjusted odds ratio, 1.12; 95% confidence interval,
1.02–1.24). There were no significant differences in the remaining secondary outcomes.
Conclusion
The findings of this study suggest that preterm cesarean delivery is not associated
with an increased risk of uterine rupture. Hence, women with 1 previous preterm cesarean
delivery (with lower uterine segment incision) should receive medical management and
counseling similar to women with previous term cesarean delivery before trial of labor
after cesarean delivery.
Key words
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Article info
Publication history
Published online: September 28, 2020
Accepted:
September 23,
2020
Received in revised form:
August 20,
2020
Received:
May 28,
2020
Footnotes
A.M. was supported by Region Stockholm. O.S. was supported by the Swedish Research Council (#21309298) and the Strategic Research Program in Epidemiology at the Karolinska Institute.
Cite this article as: Mantel A, Ajne G, Wollmann CL, et al. Previous preterm cesarean delivery and risk of uterine rupture in subsequent trial of labor—a national cohort study. Am J Obstet Gynecol 2021;224:380.e1-13.
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