A new study published in the international Nordic journal Acta Obstetricia et Gynecologica Scandinavica (AOGS) reveals that inducing labor in the weeks around term, or from week 39 to week 41, is not connected with higher rates of cesarean section compared with waiting for a later spontaneous or induced labor. There has been much debate about this in recent years with a concern that induction as opposed to expectant management might lead to a higher risk for the woman to end up with emergency cesarean section, rather than to deliver normally.
Ole Bredahl Rasmussen, MD, of Herning Hospital in Denmark and Steen Rasmussen from the Danish Medical Birth Registry, have analyzed data from the Danish Birth Registry, one of the largest such registries in the world, and made comparisons among both women who were having their first birth as well as women who had previously had a child. To obtain a good basis for the study they used a large cohort of women with securely dated pregnancies and delivering in any type of hospital, from smaller regional to large university hospitals. Data from a total of 230,528 women delivering between 2004 and 2009 were used. This is a considerably larger population-based material than used up to now in comparable studies.
Overall induction rates were 15.0% and section rates were higher among the induced compared to spontaneous labors, but after adjustment for confounding factors such as age, parity, smoking and use of epidural analgesia and adjusting for each gestational week, the results showed that in induced women, induction of labor did not convey an increased risk of cesarean section when comparing outcomes in gestational weeks 39, 40 or 41 with those women who waited longer for a spontaneous or later induced labor. The study further confirmed that there is a higher cesarean rate among the more obese women (higher BMI) and with older age in both nulliparous and parous women.
"The rate of cesarean section differs in different gestational weeks," Rasmussen notes. "Our study thus shows that it is necessary to take gestational length into account when induction of labor and expectant management are being compared." But the decision to induce labor around term seems not to be dependent on timing for success at term and during the week before or after this, when the end-point of emergency cesarean section is considered. The risk for that is either not or at best only marginally increased. Induction of labor is therefore an acceptable tool when a woman is either going past term or is presenting with a problem during her pregnancy, even if it is not a severe medical illness.
- Ole Bredahl Rasmussen, Steen Rasmussen. Cesarean section after induction of labor compared to expectant management: No added risk from gestational week 39. Acta Obstetricia et Gynecologica Scandinavica, 2011; DOI: 10.1111/j.1600-0412.2011.01160.x
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