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Uterine rupture during induced or augmented labor in gravid women with one prior cesarean delivery

Am J Obstet Gynecol 1999 Oct;181(4):882-6
Zelop CM, S(kršitelj koda) TD, Repke JT, Cohen A, Caughey AB, Lieberman E
Department of Obstetrics and Gynecology, Massachusetts General Hospital, the Department of Obstetrics and Gynecology, Brigham and Women's Hospital, Harvard Medical School, and the Department of Obtetrics and Gynecology, University of Nebras.

This paper, published in 1999, is among the most recent of the VBAC studies and we can assume that the researchers will have been familiar with previous research on the matter. Its findings are worrying.

The study looked at 2774 women attempting VBAC at term, after 1 prior cesarean delivery and no other births. It compared the rates of uterine rupture associated with spontaneous labour, oxytocin induction or acceleration, and prostaglandin E2 gel induction. The analysis controlled for other factors which might confuse the result, such as birth weight, use of epidural, duration of labour, maternal age, year of delivery, and years since last birth.

Of 2774 women in the analysis, 2214 had spontaneous onset of labor and 560 women had labor induced with oxytocin or prostaglandin E(2) gel. 1072 women had their labours accelerated ('augmented') with oxytocin.

The overall rate of rupture among all patients with induction of labor was 2.3%, in comparison with 0.7% among women with spontaneous labor. Among 1072 patients receiving oxytocin augmentation, the rate of uterine rupture was 1.0%, in comparison with 0.4% in nonaugmented, spontaneously laboring patients.

After adjusting for birth weight, use of epidural, duration of labor, maternal age, year of delivery, and years since last birth, induction with oxytocin was associated with a 4.6-fold increased risk of uterine rupture compared with no oxytocin use. Acceleration with oxytocin made uterine rupture was 2.3 times more likely, and use of prostaglandin E(2) gel made rupture 3.2 times more likely. These differences did not qualify as statistically significant though, because of the small numbers involved.

CONCLUSION: "Induction of labor with oxytocin is associated with an increased rate of uterine rupture in gravid women with 1 prior uterine scar in comparison with the rate in spontaneously laboring women. Although the rate of uterine rupture was not statistically increased during oxytocin augmentation, use of oxytocin in such cases should proceed with caution."