Labor induction after first cesarean not linked to uterine rupture
MedWire News: Labor induction is not associated with an increased risk for uterine rupture in women attempting trial of labor after cesarean section (TOLAC), US researchers say.
However, an unfavorable initial cervical exam (<4 cm dilation) is associated with an increased risk for uterine rupture during TOLAC with labor induction compared with spontaneous labor, report Lorie Harper and colleagues from Washington University in St Louis, Minnesota.
"Rather than absolutely avoiding labor induction in general, clinicians may choose to restrict labor induction to patients with a more favorable cervix exam to minimize uterine rupture risk," they write in the American Journal of Obstetrics & Gynecology.
Harper and team conducted a nested case-control study of 111 women with one previous low transverse cesarean section (LTCS) who attempted TOLAC and experienced uterine rupture (cases). These women were matched on the basis of baseline characteristics to 612 control subjects who attempted TOLAC but did not have a uterine rupture.
Uterine rupture was defined as a full-thickness disruption of the uterine wall accompanied by at least one of the following: nonreassuring fetal heart rate, hemoperitoneum, or signs of maternal hemorrhage (systolic blood pressure [BP] <70 mmHg, diastolic BP <40 mmHg, or heart rate >120 beats per minute).
Using time-to-event analysis to account for labor duration, and after adjusting for the important confounders prior vaginal delivery and maternal race, the risk for uterine rupture was not statistically different between women who attempted TOLAC by labor induction compared with those who presented in spontaneous labor, at a hazard ratio of 1.52 (95% confidence interval, 0.97-2.36).
In subgroup analyses looking at oxytocin exposure, women with induced and augmented labor were at 2.63- and 2.12-fold increased risks for uterine rupture, respectively, compared with those who completed spontaneous labor.
A secondary analysis revealed that TOLAC women who were dilated less than 2 cm and 2-3.9 cm at oxytocin initiation had a significantly greater risk for uterine rupture, at hazard ratios of 4.09 and 4.91, respectively, than those who were dilated 4 cm or more.
By contrast, women who underwent TOLAC and were dilated at least 4 cm at oxytocin initiation had a similar risk for uterine rupture to those who labored spontaneously.
"As induction of labor may take days, particularly in those with an unfavorable cervix, subjects exposed to an induction of labor may experience an increase in uterine rupture because they are at risk for a longer period of time compared to those who rapidly deliver," comment the authors.
They conclude: "Patients may be counseled that an induction of labor from a favorable cervix carries similar risks of uterine rupture as spontaneous labor."
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By Piriya Mahendra