There's a real stigma in our culture around being "overdue." That's when the text messages begin--have you had the baby yet??? Medical attitudes towards induction vary from practice to practice. To give you a sense of how much it varies, I've had clients whose providers started planning an induction for a healthy pregnancy at 40 weeks, and others who happily waited until 42. State licensure for out of hospital midwives (that is, home birth and birth center midwives) dictates that we consult with an OB at 42 weeks. I've also known healthy people with healthy pregnancies having home births who waited until 43 weeks to go into labor.
The American College of Obstetrics and Gynecology (ACOG) defines “term” as 40 weeks, with late term at 41 weeks and postterm beginning at 42 weeks. Most people begin labor spontaneously by the 42-week mark (75% by 41 weeks and 2 days). In 2013, ACOG recommended that no induction should be scheduled prior to 39 weeks unless medically indicated (because of really important things like lung maturation and brain development), and no induction should be scheduled prior to 41 weeks unless the cervix is favorable, meaning basically that it's soft and stretchy.
Yet, induction remains a routine practice, with over a fifth of births induced in 2013 (having doubled in the previous decade). According to the Listening to Mothers survey—in which half of mothers reported their labors induced either medically (41%) or by the mother herself (22%)—the primary medical concern behind induction of labor was that the parent was “overdue” (25%). Another reason given for induction is a suspected big baby, an indication that is itself rather suspect.
Since 1812, the length of pregnancy has been calculated using Naegele’s rule, which assumes that pregnancy lasts 40 weeks (280 days) from the first day of the last menstrual cycle. But research within the past few decades has questioned its standard interpretation, and challenges the use of Naegele’s rule to define term; in a 2001 study Smith found the average duration to be 283 days, which rises to 287.2 weeks for the average first time mother. And, some people have cycles that are longer than the 28 days that Naegele's rule is based on, making it an inaccurate measure of pregnancy length.
Common sense dictates that there is no single universal length of complete gestation. Rather, one should anticipate a normal range during which a healthy pregnant person will spontaneously begin labor.
Nonetheless, in that bell curve of normalcy, early term and postterm pregnancies are associated with higher risk. How great a risk is rarely explained, at least in relative terms. And one of the problems as I see it is that the risk is going to be different for healthy parents versus mothers with other risk factors, like diabetes, hypertension. There are also some very good reasons to induce, no matter how healthy someone is, for example in the case of preeclampsia.
One of the arguments my clients sometimes hear is that the complications of a "postdates" pregnancy are due to the “aging placenta,” which is conventionally understood to do a less efficient job as pregnant people reach the end of gestation. Yet recent research has questioned this idea, calling it “an uncritical acceptance of the overly facile concept.” Placentas don't just poop out automatically on a given date--and if they are less efficient, then it can be reflected by amniotic fluid volume and fundal height (which are being tracked by your provider, and can be confirmed with a Biophysical Profile).
People who are more likely to go beyond their due date include those with a higher BMI, greater weight gain in pregnancy, a first pregnancy, a baby that measures small by 10-24 weeks (identified by ultrasound), relatively longer menstrual cycles, older maternal age, stress in late pregnancy (33-36 weeks), and close maternal female relatives who also have longer pregnancies. However, each of these must be understood in terms of the parent's overall context, because we don't come out of a box all the same. The most common reason for a postdates pregnancy is inaccurate dating.
Routine induction for postdates in an otherwise healthy and normal pregnancy is performed on the assumption that risks associated with continued gestation are greater than risk associated with induction procedures. But, because induction is associated with higher rates of cesarean section, forceps and vacuum delivery, and higher use of pain medications (as well as risks associated with inaccurate dating and an induction of labor for a baby who might not be completely ready to be born), induction remains a personal choice and a balancing act.
So, what to do?
The Conversations with Your OB/Midwife
- Make it clear to your provider that you want to avoid induction unless it is medically indicated or you reach postterm. They can't make you do anything you don't want to do, and it's unethical for them to coerce you. Make it clear that you've reviewed the relative and absolute risk to your baby, and considering your excellent health during this pregnancy and your baby's healthy state, that you feel confident in waiting. It's useful to remember the ACOG definition of term and postterm. Postterm doesn't begin until 42 weeks. So, you're not postterm until 42 weeks. And so, without medical indication, why induce before 42 weeks?
What do I mean by relative vs absolute risk? Here's a nice explanation from Evidence Based Birth:
Absolute risk is the actual risk of something happening to you. For example, if the absolute risk of having a stillbirth at 41 weeks was 0.4 out of 1,000, then that means that 0.4 mothers out of 1,000 (or 4 out of 10,000) will experience a stillbirth.
Relative risk is the risk of something happening to you in comparison to somebody else. If someone said that the risk of having a stillbirth at 42 weeks compared to 41 weeks is 50% higher, then that sounds like a lot. But the actual (or absolute) risk would still be low—0.6 per 1,000 versus 0.4 per 1,000.
Yes—0.6 is 50% higher than 0.4, if you do the math! So, while it is a true statement to say “the risk of stillbirth increases by 50%,” it can be a little misleading if you are not looking at the actual numbers behind it.
- Second, discuss your Bishop's Score, which is the "favorability" of your cervix to respond positively to induction. The higher the score, the more likely you'll go into labor. A low score is associated with less likelihood to start labor, and a greater likelihood of cesarean. Here's an unofficial Bishop's Score calculator, but it gives you a sense of what to discuss with your provider. The ACOG recommends that for elective inductions, the Bishop's Score be at least an 8 out of 10. So if your score is less than 8, then why not wait a little while longer?
- Make it clear that you're willing to do kick-counts, a non-stress test (NST) and a biophysical profile (BPP) if needed to delay induction. A BPP measures four different markers of fetal well being, for a total score of 8. This is considered reliable for three days, after which you can have another BPP and keep on gestating. When combined with a NST, it's reliable for up to five days.
- Request a membrane sweep instead of a medical induction - "sweeping the membranes" refers to sweeping a finger between the interior of the cervix and the amniotic sac. Breaking that seal (but not the sac!) releases prostaglandins that ripen your cervix. Risks of breaking the sac include infection, cord prolapse, sand it puts you on a clock, so if you don't go into labor within a certain period other interventions will be used, increasing the risk of cesarean.
- Keep it positive, say that you understand what they're saying and that you're taking it into consideration, but that you feel confident in your decision. And if you want to go for it, you can say that you're willing to sign something saying that you're going "against medical advice" if necessary.
What You Can do to Get Labor Going
Unless your body is ready, basically we can't force it to have a baby. However, what we hope for in using tricks to self-induce is that you're close enough to the borderline to just nudge your body into labor. To get things going yourself:
- Acupuncture. Studies show this is especially useful in ripening the cervix.
- Acupressure point stimulation.
- Nipple stimulation, ideally with a breast pump (or get your toddler to nurse!). Pump 10 minutes per session, 4 sessions per hour. You may need to do this multiple times, and it works especially well when you're already cramping. Stop if contractions start.
- Chiropractic care (sometimes it's helpful to get the baby into an optimal position to get the right kind of pressure against your cervix).
- Homeopathic caulophyllum 30C 3x daily for two days, then again three days later if needed, or alternating doses of caulophyllym 30C and cimicifuga 30C for two days.
- Sex (and orgasms), because semen has helpful prostaglandins that can ripen the cervix, and it's more fun than castor oil.
- Castor oil. I'd recommend doing this under someone's guidance.
There may come a point when you're just done and nothing seems to be working. It's up to you, and there's no one saying that you need to wait it out until you've been pregnant for a whole year (j/k). All of this is to say that you can use this information as you wish, do your research, and make your own choices.
Further Reading & Resources
- For more excellent information, check out this wonderful post from midwifery professor Rachel Reed on induction, and her post on what to expect during an induction. Or, listen to her interview on the Yoga Birth Babies podcast, episode #7.
- Evidence Based Birth - The Evidence on Induction for Going Past Your Due Dat
- Evidence Based Birth - What is the Evidence for Induction or C-Section for a Big Baby
- Evidence Based Birth - Evidence On: Induction of Labor When Your Water Breaks at Term
 Jukic et al. “Length of human pregnancy and contributors to its natural variation,” Human Reproduction (2013), Vol. 28, No. 10, pp. 2848-2855.
 Baskett, Thomas F. and Nagele, Fritz. “Naegele’s rule: a reappraisal,” BJOG (2000). Vol, 107, No. 11 pp. 1433-1435; Boone, Cosette, “Establishing Estimated Date of Birth (EDB),” ACNM Clinical Bulletin, December 2000, accessed December 20, 2015; Smith, Gordon, “Use of time to event analysis to estimate the normal duration of human pregnancy,” Human Reproduction (2001), Vol. 16, No. 7 pp. 1497-1500.
 Halloran, et al. “Effect of Maternal Weight on Postterm Delivery,” J Perinatol (2012), Vol. 32, No. 2, pp. 85-90; Jucik et al, “Length of human pregnancy and contributors to its natural variation,” Hum Reprod (2013), Vol. 28, No. 10, pp. 2848-2855; Oberg et al. “Maternal and Fetal Genetic Contributions to Postterm Birth: Familial Clustering in a Population-Based Sample of 475,429 Swedish Births,” Am. J. Epidemiol (2013), Vol. 177, No. 6, pp. 531-537; Olesen et al. “Perinatal and maternal complications related to postterm delivery: a national register-based study, 1978-1993,” Am J Obstet Gynecol (2003), Vol. 189, No. 1, pp. 222-227; Margerison-Zilko et al. “Post-term birth as a response to environmental stress,” Evol Med Public Health (2015), no. 1, pp. 13-20; Johnsen et al. “Fetal size in the second trimester is associated with the duration of pregnancy, small fetuses have longer pregnancies,” BMC Pregnancy Childbirth (2008), Vol. 8, No. 25.
 Bennett KA, Crane JM, O'shea P, et al. First trimester ultrasound screening is effective in reducing postterm labor induction rates: a randomized controlled trial. Am J Obstet Gynecol. 2004 Apr. 190(4):1077-81.