Are C-Sections Linked to Inducing Labor?


This study compares Cesarean risk factors by week of pregnancy between induced labor and waiting under observation to assess the need for being induced. Aggregated data from 230,528 deliveries between 2004 and 2009 were studied. In this study, first-time deliveries and non-first-timers were compared. The gestational week, decision to induce labor or wait until delayed spontaneous or induced labor, and whether a Cesarean section was needed were recorded. The results showed that Cesarean risk after gestational week 39 was the same across all women, regardless of the strategy for labor and how many full-term deliveries they had.

The risk of Cesarean delivery is higher in women with artificially induced labor than in those with spontaneous labor. Hence, the choice is between inducing labor and waiting under observation, known as delayed induction (“expectant management”). Previously, the Cesarean risk was compared between women who underwent induced labor after a particular week in pregnancy and those who underwent expectant management. In women delivering for the first time, the risks were significantly less for induced labor after a specific gestational week than in delaying the induction. In non-first-timers, the risk of Cesarean was the same in both. There exists contradictory reports about the risk factors upon labor induction before and after 41 gestational weeks. This study suggests a new way of analyzing data on the two strategies.

* The birth registry databank of Denmark was used to compare labor induction strategies and records of Cesareans among 230,528 deliveries chosen based on certain eligibility criteria.
* The mother’s age, body mass index, use of epidural during labor, and smoking habits were recorded. The data included estimation of fetal age and delivery date based on ultrasound scan.
* First-time mothers and non-first-timers were analyzed independently. Each group was divided into “induced labor” and “waited for delayed labor” groups, and their gestational weeks were recorded.
* The Cesarean rates were calculated and statistically compared.

* The gestational week during labor, choice of epidural and weight index during pregnancy were significantly different between the two groups.
* The results showed that 7.3 percent of all deliveries were Cesareans and 15 percent of the deliveries were induced labors. Among the women who had induced labor, 14.5 percent had Cesareans, while spontaneous labor resulted in 6.1 percent Cesareans.
* More first-timers had Cesareans than non-first-timers (12.8 percent as opposed to 2.3 percent, respectively) and they chose epidural more often.
* It was found that until the gestational week 38, the Cesarean risk was higher for induced labor than delayed labor (expectant management). The risk was equal in both the groups from week 39 onwards.

Shortcomings/Next steps
In this study, analysis of spontaneous labor in the same week as induced labor or induction during spontaneous labor (in case of ruptured membranes) can be included by measuring half weeks. Women who chose a Cesarean section should also be included together with the gestational week data. Cervical status (dilation) is not included in this analysis.

The risk of Cesarean after induced labor does not significantly increase after pregnancy week 39. Many large-scale studies conducted across the world agree on week 41 as the period when labor induction does not increase chances of cesarean. The cesarean rates in Denmark are lower than those in the United States, even when the rates of induction of labor are the same. While not going into a spontaneous labor is not a serious medical emergency, this analysis together with the previous studies provides a good indication for medical care providers to advise induction without an increased risk of cesarean. However, other medical complications after week 39 must be considered before counseling induction.

For More Information:
Cesarean Section after Induction of Labor Compared with Expectant Management: No Added Risk from Gestational Week 39
Publication Journal: Acta Obstetricia et Gynecologica Scandinavica, 2011
By Ole Bredahl Rasmussen, MD; Steen Rasmussen; Hospital Unit Vest, Herning, Denmark; National Board of Health, Copenhagen, Denmark

FYI Living Lab Reports are a summary of the original report.

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