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Delivering the Odds on Childbirth

labor induction countdown

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Most expectant women, whether they’re having their first baby or they’ve gone through the labor and delivery process before, have some kind of plan in mind for how they’d like to deliver their baby. But, nature doesn’t always let things go according to plan. Annually, nearly 1 million women in the United States end up having an unplanned labor induction. Induction may be required when there are signs of an infection, the placenta starts to separate from the uterus, or pregnancy has hit the 42-week mark, and taking steps to speed things along is often the best way to keep a mother and baby safe and healthy.

Labor can be induced in a variety of ways, but even after induction, labor can still take a long time – anywhere from a “mere” two to three hours, to several days. And some babies can seem downright stubborn: nearly one-third of women who have labor induced will still need a Cesarean section. Though doctors have identified multiple risk factors for failed inductions, doctors still have no way of knowing when and for which patients an induction will work, especially if the mom-to-be’s cervix isn’t in the textbook state for delivery readiness – for instance, it may not be dilated enough, too firm, or too short.

“As advanced as the field of obstetrics has become, there are still a lot of mysteries surrounding pregnancy and labor,” said Lisa Levine, MD, MSCE, director of Penn’s Pregnancy and Heart Disease Program and an assistant professor of Obstetrics & Gynecology. “During labor, the cervix goes through many gradual changes, including softening, shortening, and thinning. It’s the body’s way of preparing to deliver a baby. But for reasons still unknown, for many women, these natural changes just don’t happen.”

induction calculator
But, a new online Labor Induction Calculator developed by Levine and colleagues is helping providers guide patients as they make decisions about their care, and offers a personalized approach to counseling women and families about the risks associated with of Cesarean section after undergoing an induction. Cesarean delivery and lengthy and failed inductions increase a woman’s risk of infection and bleeding complications, both of which underscore the critical need for a way of predicting which inductions will result in cesarean delivery and longer labor earlier in the induction process.

The “calculator” – a predictive model for cesarean delivery – was developed by examining risk factors for failed induction in nearly 500 women whose labor was induced. By understanding key factors such as Body Mass Index at delivery, height, and gestational age at induction, the team developed an online tool that care providers can use to calculate the likelihood of a cesarean delivery for women with a so-called “unfavorable” cervix.

“It’s a way for providers to try and see into the future, counsel patients with more insight, and adjust care plans and patient expectations accordingly,” Levine said.

Currently, the Bishop Score is the most commonly used method to rate the readiness of the cervix for induction of labor. Originally developed to evaluate the likelihood of vaginal delivery in women who have given birth before, it is also now used for women who have never given birth and who are being considered for induction of labor. First published in 1964 by Edward Bishop, MD, the Bishop score considers five different components of a vaginal exam to arrive at a total score ranging from zero to 12. A lower score indicates that an induction is less likely to be successful, while a higher score suggests labor will most likely start spontaneously (and soon). It also suggests that if an induction is necessary, it will more than likely be successful.

Levine’s calculator is intended for use among women undergoing a full term induction of labor with an unfavorable cervix, and no prior history of Cesarean delivery. The tool is useful for assessing any woman, regardless of whether she’s had children previously.

“Let’s say for example, we have a woman who is having her first child, is 39 weeks pregnant and 65 inches tall, with a BMI of 29kg/m2, and a Bishop score of four at induction,” Levine said, plugging the data into the calculator. “Her probability of a cesarean delivery is 19.3 percent. On the other hand, if we have a woman who has had children previously, is 41 weeks pregnant, 63 inches tall with a BMI of 40 kg/m2, and has a Bishop score of three, her probability of a cesarean delivery is 31.7 percent.”

Levine says the team is also interested in learning whether the calculator will improve patient satisfaction with the induction and delivery process, and provider communication by providing additional information about their birth plan, helping to manage their expectations, and keeping them more involved throughout the process. She notes that it’s important that tools like the new calculator are used to augment patient counseling and guide patient expectations and should not be used in isolation to make care decisions. Though with more than 20 percent of pregnancies requiring induction in the United States annually, she says it’s “critical to be able to appropriately counsel patients and families about the risks and benefits of induction.”

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