Article

Induction of labor and cesarean delivery by gestational age

Department of Obstetrics and Gynecology, Stanford University, Palo Alto, California, United States
American journal of obstetrics and gynecology (Impact Factor: 3.97). 10/2006; 195(3):700-5. DOI: 10.1016/j.ajog.2006.07.003
Source: PubMed

ABSTRACT Studies of cesarean delivery (CD) rates among women undergoing induction of labor (IOL) often compare such women to women experiencing spontaneous labor at similar gestational ages. We sought to examine the association between IOL at various gestational ages and CD, accounting for the effect of increased gestational age among the comparison group who were managed expectantly.
We conducted a retrospective cohort study of all term, singleton, cephalic presentation pregnancies delivered at our institution over 15 years excluding cesarean deliveries before labor. For each gestational age of induction, we created a comparison group of women who were undelivered at that gestational age, and who experienced labor at some future gestational age.
In women undergoing IOL at 38 weeks gestation, the CD rate was 11.9% as compared to 13.3% (P = .42) of women beyond 38 weeks gestation. The CD rate for induction of labor compared to ongoing pregnancy was 14.3% versus 15.0% (P = .62) at 39 weeks, 20.4% versus 19.0% (P = .41) at 40 weeks, and 24.3% versus 26.0% (P = .39) at 41 weeks. When controlling for potential confounding, there was a higher rate of CD among women with expectant management beyond 38 weeks (adjusted odds ratio [AOR] 1.80; 95% CI 1.29-2.53), 39 weeks (1.39; 95% CI 1.08-1.80), and 40 weeks (AOR 1.27; 95% CI 1.00-1.62).
Our findings suggest that IOL may not increase a woman's risk of CD when compared to expectant management. While this question has been addressed prospectively at 41 weeks gestation, it requires further examination at earlier gestations and among various subgroups.

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    • "When the issue of outcome by week of gestation is the primary outcome to be examined, careful choice of the appropriate denominator is paramount as demonstrated both in the work on stillbirth and induction of labor [7,25] However, in the setting of interventional trials, this is less important. Certainly, the most important issue is that for any study, careful attention be paid to choosing the appropriate outcome measures and how best to measure them. "
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