Why is induction recommended over age 35?

What is induction?

Induction is using medical means to start a labor that hasn’t started on its own. (Learn more about methods of medical induction.)

Induction may be recommended if: the baby is not growing well or thriving in utero, the parent has an illness that is worsening (such as diabetes or hypertension), the baby is overdue, or the bag of water broke and labor hasn’t started on its own. There is also a category called elective induction, which is being induced for non-medical reasons, such as wanting to control the timing of the birth or being tired of being pregnant.

As with all medical interventions, induction has benefits and risks. If there is a clear medical indication that delivering the baby sooner rather than later would have more benefits than the risks of induction, then induction is recommended.

How Common is Induction

Induction rates rose steadily from 1990 to 2010 ((source for chart), then somewhat plateaued, following some active campaigns to reduce elective induction, such as AWHONN’s “Don’t Rush Me – Go the Full 40” about the physiologic benefits of full-term pregnancy, and an editorial in American Family Physician about stopping elective induction before 39 weeks to reduce unintended harms to babies not yet ready for birth.

In 2014, ACOG’s recommendation was to induce at 41 weeks.

That changed after the results of the ARRIVE trial were published in 2018. The ARRIVE trial was considered a high quality randomized controlled clinical study (although ACNM did caution against over-generalizing the results, this article addresses methodology concerns, and this infographic addresses how the results might not apply to all people.)

The results of that trial (and other trials) were that elective induction decreased the risk of cesarean. (Rates were 18.6% in the induction group versus 22.2% in those assigned to the wait for labor to begin group.) The induction group was also less likely to have gestational hypertension / preeclampsia (9% vs 14%).

ACOG (the American College of Obstetrics and Gynecology) issued guidance in response, and a joint statement from ACOG and SMFM (Society for Maternal Fetal Medicine) said ““ACOG and SMFM have … determined that it is reasonable for obstetric care providers to offer an induction of labor to … Women who are planning their first delivery, are healthy and have no medical or obstetrical complications… who are 39 weeks pregnant and had an ultrasound performed early in the pregnancy to confirm dating.”

In other words, elective induction at 39 weeks is back on the table as an option after 2018. In 2016, 24.5% of US births were induced. In 2021, 32% were.

There was not universal agreement with this recommendation: WHO says there’s insufficient evidence to recommend elective induction before 41 weeks and NICE says induction should be offered at 41 weeks. SOGC (Society of Obstetricians and Gynaecologists of Canada) said we shouldn’t recommend induction just to reduce cesarean risk, ACNM (American College of Nurse Midwives) said there are benefits of spontaneous labor and risks of induction and other effective ways to reduce the risk of cesarean (e.g. doulas, midwifery care, movement during labor)

Is induction recommended for parents over age 35?

In a 2022 consensus statement on Pregnancy after Age 35, ACOG made a more explicit move to recommend induction for older moms: “We recommend proceeding with delivery in well-dated pregnancies at 39 0/7–39 6/7 weeks of gestation for individuals with anticipated delivery at age 40 years or older due to increasing rates of neonatal morbidity and stillbirth beyond this gestational age.” A randomized trial of induction at 39 weeks for women over 35 also indicated no increased risk of cesarean and no short-term adverse effects on mothers or babies.

Stillbirth Risk

How high is the risk of stillbirth for mothers over age 35? How much higher is it if the pregnancy continues past 39 weeks?

This chart (source) compares the risk of stillbirth per 10,000 pregnancies during each week of pregnancy for pregnant people under age 35 vs. for people 35 years or older. It is clear that the risk does increase each week, and that it is much higher after age 35.

Weeks	<35 yrs	>35 years
39	3.9	5.0
40	6.8	10.0
41	8.5	15.4
42	28.2	32.5

[Note: if you’re a pregnant person reading this, I know that numbers like this can be frightening. Take a deep breath, and flip the numbers: even a rate like 32.5 per 10,000 means that 9,967 out of 10,000 will NOT have a stillbirth in week 42.]

Benefits and Risks of Induction

So, the research cited above indicates that inducing at week 39 may reduce the risk of stillbirth, possibly reduce the risk of cesarean, and can reduce the chance of hypertension or diabetes worsening.

What else does the research show us about the risks and benefits of induction? A Cochrane review, which mostly looked at induction at 41 weeks vs. continuing to the 42nd week, showed:

• fewer perinatal deaths / stillbirths
• better Apgar scores at birth, and fewer NICU admissions
• little to no difference for: perineal tears, postpartum hemorrhage, breastfeeding at discharge

But, induction is not innocuous. What are the risks or tradeoffs of induction?

• Medicalization: An induced birth is inherently more medicalized than waiting for labor to begin spontaneously – continuous fetal monitoring is required, IV fluids are common – these two factors can also reduce the birthing parent’s ability to move around and use natural coping techniques. Plus they may not be allowed to eat solid foods. ACNM summarizes this as “Based on US practices, induction may not be a desirable option for those persons who prioritize a… low-intervention birth experience.”
• Not waiting for baby to trigger labor: In the final weeks of pregnancy, babies are gaining immunities, gaining weight, increasing their brain development and maturing their lungs. When the baby’s lungs are mature, that triggers hormones that trigger labor. If we induce labor before that happens, there is a chance that baby is not as ready for birth as they would be if labor started spontaneously. At 39 weeks, many babies are totally ready to go, but not all.
• Longer labor / hospital stay: In late pregnancy, prostaglandins cause the cervix to ripen and thin. If we jumpstart labor, the body may not have made these preparations for labor. So, with an induction, it can take a while to get labor started. It might take 12 – 24 hours, or longer if cervical ripening is needed. If an induction takes too long, cesarean may be recommended.
• Changes to the hormonal dance of labor. Typically, in late pregnancy, the uterus becomes more sensitive to the oxytocin hormone which causes labor contractions. During labor, as the cervix stretches, pain receptors in your brain release endorphins, a natural painkiller more effective than morphine. When labor is induced with Pitocin (synthetic oxytocin), your body does not produce as much natural oxytocin and does not produce as much endorphins, so you miss out on that natural pain relief. (Learn more about the hormonal differences.)
• More Pain? I have not been able to find any research comparing average pain levels in an induced labor versus a spontaneous labor. (Nor much on maternal satisfaction, although it seems to me that both of these things are important factors that we should be researching.) Anecdotally, many people seem to experience more pain in an induced labor. That may be partially due to the fact that a natural labor builds intensity gradually, allowing you to adapt and find coping techniques thar work for you. With a Pitocin induced labor you jump straight into long, strong contractions. (3 – 4 contractions in ten minutes, each lasting 40 – 60 seconds.)
• Induction can cause variations in the baby’s heart rate, which can lead to additional interventions.

Questions to Ask

If your care provider has offered induction at 39 weeks, here are some questions you can ask yourself or them to decide if it’s right for you:

• Are there other ways to reduce risk of stillbirth or monitor for other problems with my baby?
  • Learn about fetal movement tracking – paying attention to your baby’s kicks can reassure you that all is well.
  • Ask about tests to monitor baby’s well-being, such as the non-stress test, biophysical profile
• Are there other ways to reduce the chance of cesarean birth? There are: having continuous labor support (especially from a doula), upright positions and movement during labor and birth, choosing a midwife rather than an OB as your care provider and waiting until 6 cm dilation before being admitted to the hospital are just a few. (Learn more.)
• Are there non-medical ways to get labor started? Possibly sexual intercourse, definitely breast / nipple stimulation, possibly acupuncture, herbs, or castor oil. If the need to start labor is urgent, your care provider may tell you these aren’t effective enough. But, if you have some time, they may say these are options you could try.
• How likely is induction to be successful? If you’re almost ready to go into labor on your own, induction will be faster and more effective than if you’re not. So, learn about the Bishop score which measures ripening and effacement of the cervix and ask your caregiver what your score is. Starting Pitocin only when you have a Bishop score of 4 increases the chance of cesarean. Waiting for your cervix to get ready naturally, or using cervical ripening methods to get your Bishop score up to 8 or higher (if it’s your first baby, 6 or higher if you’ve given birth before) will increase the chance of a successful induction. (Learn more about this and other factors here.)

How to have the best possible induction?

If you do decide that induction is the best answer for you, here’s how to increase your satisfaction:

• Ask your care provider what method(s) will be used, and learn more about them.
• Be prepared for a long process. Pack some entertainment options and plenty of patience. Consider having an extra support person so they can swap off or take breaks.
• Eat before your induction begins, as you may not be able to eat after it begins.
• Create an environment that is as calm and soothing as possible: perhaps dim light, music playing, favorite items to wear or look at or hold.
• Try to be as mobile as possible (this helps baby rotate and descend which helps labor to progress.) For example, try sitting on a birth ball or in a rocking chair rather than lying in bed.

Learn more about interventions in maternity care and making informed choices in episode 8 of the Transition to Parenthood Podcast, or by reading Pregnancy, Childbirth, and the Newborn: The Complete Guide.

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