Induction Why? or Why Not?

Case controlled studies show no benefit to inducing for postdates

leo_orig_edited.png

© 2012 By Rebecca Dekker, PhD, RN, APRN  www.evidencebasedbirth.com.
The author of this article is Rebecca Dekker for more information contact her directly email: evidencebasedbirth@gmail.com
I’ve written before about the lack of evidence for continuous electronic fetal monitoring, but recently I felt the need to write further on this issue. I feel strongly that our maternity care in the U.S. has headed down the wrong path with fetal monitoring. Yes, I believe that it is beneficial to monitor a baby’s heart rate during labor. But the majority of American women receive the wrong type of fetal monitoring for their situation. They receive something called continuous electronic monitoring instead of intermittent auscultation. 

But what’s the big deal? Well, first of all, everybody else in the world tends to follow our example. U.S. hospitals have invested over $700 million dollars in electronic fetal monitoring equipment that is NOT evidence-based and contributes to unnecessary Cesarean deliveries. Do you think developing countries around the world should be following our example, spending precious resources on this equipment? Second, most women in our country do not give informed consent for electronic fetal monitoring. The vast majority of women in the U.S. have no idea about the benefits and risks of the #1 most common obstetric procedure used in labor and delivery– electronic fetal monitoring.

One of my readers recently told me that she was going to request intermittent auscultation (the evidence-based option for fetal monitoring) from her care provider—and her doctor agreed! We were both curious to see how the hospital would react to her seemingly benign request for evidence-based monitoring.

I’ve decided to break this topic into two articles. In this article, I will discuss the evidence for fetal monitoring. In my next article, I will share with you one mother’s quest for evidence-based fetal monitoring, and talk about how other pregnant women can follow her example. You can read the next article that shares my reader’s story here.

What are the different types of fetal monitoring?

Electronic fetal monitoring (EFM) is when you use a Doppler ultrasound machine to monitor the baby’s heart rate while simultaneously using a pressure sensor to monitor the mother’s contractions. Both of these sensors are linked to a recording machine, which shows a print-out or computer screen of the baby’s heart rate and the mother’s contractions. (Alfirevic, Devane et al. 2006). There are 2 types of EFM: continous and intermittent.
 

  • According to the 2007 “Listening to Mother Survey,” 87% of U.S. described experiencing continuous electronic fetal monitoring during labor (Declercq, Sakala et al. 2007). However, just because the monitoring is continuous does not mean that a clinician is continuously watching the monitor. Most of the time, a clinician determines and evaluates the fetal heart rate every 30 minutes during the active stage of first stage labor (when the mother is dilated 5-10 cm) and every 15 minutes during the active pushing phase of labor.  However, if the mother is high risk, or if she is being given Pitocin, then this may be done more frequently (ACOG, 2009).

  • In 4% of U.S. women, EFM is used only intermittently during labor (Declercq, Sakala et al. 2007). This is called intermittent electronic fetal monitoring, and it generally means that you have to wear the machine sensors for 20-30 minutes of every hour (I could not find any guidelines that recommend a specific frequency and length of intermittent EFM).

Intermittent auscultation is used with 3% of U.S. women during labor (Declercq, Sakala et al. 2007). With intermittent auscultation, the care provider listens to the baby’s heart rate for about 60 seconds using a fetal stethoscope (fetoscope or Pinard) or a hand-held Doppler ultrasound device. While listening, the care provider also palpates the mother’s contractions by placing a hand on the abdomen. Most guidelines agree that intermittent auscultation should be done every 15-30 minutes during the active phase of the first stage of labor (from 5-10 cm dilation) and every 5-15 minutes during the pushing phase of the second stage of labor (AWHONN, 2008).

What is the purpose of using these tests?

Theoretically, the purpose of monitoring the baby’s heart rate during labor is to identify oxygen problems in the baby so that you can intervene and prevent complications

So which method is better for a woman in labor?

Based on the evidence, the best option for most women and babies is intermittent auscultation.

In a Cochrane review (Alfirevic, Devane et al. 2006), researchers compiled the results of 12 randomized, controlled trials with more than 37,000 women. Unfortunately, many of the studies were of poor quality—however, 2 of the studies were of excellent quality. In all of these studies, women were randomly assigned to either receive continuous EFM or intermittent auscultation. These classic research studies took place mostly in the 1970′s and 1980′s– meaning that this evidence has been around for at least 30 years.

There were no differences between women who received intermittent auscultation and those who received continuous EFM in perinatal mortality, cerebral palsy, Apgar scores, cord blood gasses, admission to the neonatal intensive care unit, or low-oxygen brain damage. These findings were consistent in both low-risk and high-risk women. There was a lower risk of newborn seizures in the continuous electronic fetal monitoring group; however, overall, seizure events were very rare (0.2%)

Women in the continuous EFM group were 1.7 times more likely to have a Cesarean and were slightly more likely to have a forceps/vacuum delivery when compared to women in the intermittent auscultation group. Women in the continuous EFM group were also more likely to require pain medication.

Interestingly, the researchers found an interaction between Cesarean rates and continuous EFM. This means that in hospitals where there are higher Cesarean rates, continuous EFM may lead to an even higher risk of Cesarean delivery.

As stated earlier, one of the purposes of continuous EFM is to prevent cerebral palsy. However, researchers have found that continuous electronic fetal monitoring is a very poor test for this purpose. False positive rates for predicting cerebral palsy are as high as 99.8% (that’s basically 100%), even in the presence of “ominous signs,” such as multiple late decelerations or decreased variability (Nelson, Dambrosia et al. 1996).

The evidence against continuous electronic fetal monitoring is so clear that the U.S. Preventive Services Task Force issued a recommendation saying that continuous electronic fetal monitoring should NOT be used in low risk women. Even ACOG has endorsed intermittent auscultation as an “appropriate and safe alternative” to electronic fetal monitoring (ACOG, 2009).

My doctor says that they will just “put me on the monitor” for 20 minutes of every hour. Is that any better than continuous electronic monitoring?

There is no evidence that intermittent monitoring with the electronic fetal monitor is any better than continuous electronic monitoring. In one study (Herbst & Ingamarsson, 1994),  researchers randomized more than 4,000 high-risk women to receive either continuous EFM or intermittent EFM. They defined intermittent EFM as being on the monitor for 10-30 minutes every 2 hours, with stethoscope auscultation every 15-30 minutes in between monitoring periods. The researchers found no differences in any outcomes.

There are no studies that compare intermittent EFM with intermittent auscultation. However, because intermittent auscultation is superior to continuous EFM—and continuous EFM and intermittent EFM have similar outcomes—it is possible that intermittent auscultation is also better than intermittent EFM.

I don’t think I mind wearing the electronic monitor. What harm could it really do?

To make a fully informed choice, you need to understand the risks and benefits of the electronic fetal monitor. Compared to intermittent auscultation, continuous EFM has the benefit of a decrease in the risk of newborn seizures (a rare outcome). However, it also increases the risk of Cesarean delivery, increases the risk of forceps/vacuum assistance, and increases the risk that you will need pain medication.

In addition to these risks, EFM restricts your ability to walk and change positions. Even a portable or “wireless” monitor is cumbersome, restricts the ability to use water immersion to ease pain, and likely carries with it the same risks as regular EFM. Watching the monitor can create fear and distraction. Many caregivers watch the monitor instead of actually watching and caring for the laboring woman! A fundamental principle that we teach nursing students in nursing school is “Look at your patient, not the monitor.” Having a monitor in the room makes it easier for people to focus on the monitor, not the mother and baby. It also makes it easier for the nurse to monitor the woman from outside the room—possibly decreasing the amount of support a woman could get from her nurse.

If intermittent auscultation has the best outcomes, why don’t more hospitals use it?

Liability. Various hospital administrators need the electronic recording archived in their computer database in case of a lawsuit. With intermittent auscultation, the care provider can document what they hear, but there is no “strip”—there is no continuous electronic recording.

Lack of resources. Many hospital labor and delivery units may own only 1 or 2 handheld Dopplers—or none at all—and if they do own one, it may have “walked off” and can’t be found anywhere on the unit.

Time. The nurse, midwife, or doctor has to actually be at the bedside of the woman every 15-30 minutes and take a minute or two to listen to the heart rate while palpating the contraction. It is easier for nurses to just look at the monitor on a screen at the nurse’s station.

Big Business. Electronic fetal monitoring is a big business. There are approximately 28,000 fetal monitors in more than 3,400 hospitals in the US, representing an investment of over $700 million dollars. I find it interesting that hospitals can spend more than $200,000 per hospital on electronic monitor systems, but they cannot afford to pay $400-500 a piece for handheld Dopplers to use with intermittent auscultation. Electronic fetal monitoring is the perfect example of high-tech, high-cost, low evidence-based care.

Clinical experience. Many doctors and nurses have never used a fetal stethoscope (some do not even know they exist). Some OB’s may have never even heard of intermittent auscultation. Although OB’s seem to be comfortable using a handheld Doppler to listen to the baby’s heart rate during prenatal appointments, many have never had any training or experience in using this technique during labor. As one doula told me, “I have yet to meet an OB or nurse that even knows what a fetoscope is let alone how to use it, and I’ve never seen an OB or nurse use a Doppler outside of prenatal appointments.” Nurses and OB’s are much more comfortable using EFM, since they have probably had a lot of training and experience with it. In summary, as one midwife wrote on her own blog… “You CAN say no to the fetal monitor, but you’ll need to bring your own Doppler—and nurse.”

Lack of leadership from ACOG. In their 2009 practice guidelines for fetal monitoring, ACOG states that “despite the frequency of its use, limitations of EFM include poor interobserver and intraobserver reliability, uncertain efficacy, and a high false-positive rate (pg. 193).” EFM--even though the research evidence overwhelmingly supports intermittent auscultation, and this evidence has been around for more than 30 years now. The American College of Nurse Midwives openly disagrees with ACOG and says that intermittent auscultation– not electronic monitoring– should be the preferred method.

Judy Slome Cohain, CNM There is a low risk of stillbirth at ≥42 weeks in the US although it is even lower in Europe.  Once you get to term, the chance of a healthy woman delivering a live baby is 99.95% in Europe and 99.90% in the US. If post-term induction were to be shown in the future to have the capability of preventing stillbirth without increasing brain damage and perinatal mortality, about 2,000 healthy, low risk women would have to be induced at 40 weeks to prevent one stillbirth.

Stillbirth and Neonatal death happen throughout pregnancy (1,2).

Term stillbirth and perinatal mortality rates: European rates in red , US rates in blue

Week Stillbirth/1000 undelivered Neonatal deaths/1000 live births 37 1/3000         1/1400 2.7/1000 38 1/2500         1/1250 1.5/1000 39 1/1800         1/1000 0.9/1000 40 1/1300          1/800 0.7/1000 41 1/800            1/750 0.9/1000 42 1/600            1/900 1.3/1000 It is expected that 98% of women do NOT deliver on their due date, but rather 49% before and 49% after their due date, and only 2% on their due date. Since first births on average deliver a week after the due date, about 75% of first births deliver after their due date.  Data from 2002-2008 in the US showed  11.4% of low risk first births and 6.4% of low risk multiparous births that attempted vaginal birth were induced for the reason of  'postdates’ and a total of 45% of births, that were not elective cesareans, were induced.

Inducing for postdates originated from an uncontrolled, non-randomized observational study from 1999 showing a drop of 1/1000 in the stillbirth rate at several hospitals, occurring serendipitously during the same time frame as an increase in the induction and cesarean rates in Canada.  The drop in stillbirths in this type of research can be explained by a change in many other possible variables that took place during the same time period. This result has never been shown by case controlled trials. The best quality evidence says that induction for postdates does NOT reduce the number of stillbirths or improve perinatal mortality rates.

The best quality evidence says that induction for postdates does NOT reduce the number of stillbirths or improve perinatal mortality rates.

Documented Drawbacks of routine induction: High induction rates are associated with an increase in premature births between 34–36 weeks, increased births of problematic babies that need intensive care,  higher cesarean rates and 1 in 3000 maternal deaths due to cesarean, a possible increase in brachial palsy due to undo force of induced contractions, and two fold increase in amniotic fluid embolism.

There is some logic behind a desire to deliver In Vitro Fertilization (IVF) pregnancies at 40 weeks to avoid the rare cases of stillbirth that take place after 40 weeks. Since you know when fertilization took place, you know when the fetus is fully developed.  IVF babies are particularly precious since they may not be replaceable. There is some logic behind delivering uncontrolled diabetics early to avoid stillbirth for similar reasons. 

The same cannot be said for non-IVF pregnancies. Ultrasound dating is only accurate to the nearest 2 -4 weeks. A woman who thinks she is 40 weeks by 10 week ultrasound, might only be 36 weeks and if induced, the fetus may need intensive care, and therefore would be more vulnerable to problems such as infection.  About  90% of pregnancies currently defined as post term would not be so if instead of rounding out pregnancy to 40 weeks (280 days) it was counted as 284 days.  When 284 days are used to define pregnancy instead of 280, less than 1% spontaneously deliver ≥2 weeks late, rather than 10%. 

If a prenatal test could predict which pregnancies would end in third trimester stillbirth, then doctors could do the test and induce those pregnancies. But, no prenatal test has been shown to predict stillbirth, therefore doctors are only left with the option of inducing all postdate births or none of them.   

First births on average deliver at 41+0 weeks or 287 days.  In the absence of any other explanation for delayed birth in primiparous women, this phenomenon appears to be explained by the increased level of anxiety of women on their first pregnancies. Women who want to finish a doctoral thesis, attend a wedding, or an important event are well known to deliver after their desired action is finished. Women who go past 42 weeks either have incorrect dating, a wedding they don’t want to miss etc., or fears directly or indirectly related to the birth, family or mothering that have not been dealt with.

Having warm care providers available helps prevent prolonged pregnancy and therefore stillbirth. Having one-on-one midwifery model ongoing support in which fears are expressed and dealt with, the mother starts birth informed and knowing that the person they want will be available and attending the birth, and the same stillbirth rates and perinatal mortality are obtained with much lower cesarean rates, as with medical management with routine induction at 41 or 42 weeks.

What is the research evidence Postdate induction is based on unreliable ultrasound dating. Pregnancy is about 284 days not 280.

The only pregnancies in which the approximate time of fertilization is known are In Vitro Fertilization (IVF) pregnancies.  The fertilization of IVF pregnancies is known to take place somewhere within 18 hours of combining egg and sperm in the Petri dish. This knowledge of fertilization has been used in studies to see how accurate first trimester ultrasound is in establishing due date.

Ultrasound specialists, blind to conception date of IVF pregnancies, were only able to estimate the age of the IVF pregnancies within -15 days and +14 days of the actual known due date in the first trimester. (4)  Among accurately dated IVF pregnancies, if ≥284 days were used to define pregnancy, instead of ≥280 days, in the absence of induction, post term pregnancies would account for less than 1% of pregnancies (4).  That means that if pregnancy is considered 284 days instead of 280 days, less than 1% of women would go beyond 42 weeks, instead of about 10%.

According to the 1980 edition of Williams Obstetrics Textbook, published before the widespread use of labor induction for postdates, 10% of pregnancies persist for 42 weeks or more. In a large study done with the intent to reduce post term pregnancy using ultrasound, the post term rate was reduced to 2.5%(5). However, in a 2010 study from Sweden using a population of over 1,175,000 singleton births from gestational week ≥37, for which 95% had first trimester ultrasounds, 9% of pregnancies still persisted for 42 weeks or more (6).

In a study of 17,000 Finnish women from 1993–98 trying to prove the usefulness of ultrasound dating between weeks 8 and 16, 10% of women went post term. (7). When two days were added to the length of pregnancy from LMP, only 6% of deliveries were post term(7). This is the only study of first trimester ultrasound that also looked at outcomes, and it found no increase in perinatal mortality among deliveries after 42 weeks. 

Research comparing induction to waiting Stillbirth and perinatal death occur at every week of pregnancy.  BUT induction of labor at any week has not been shown to decrease stillbirth or overall perinatal mortality and may increase maternal and newborn morbidity. The stillbirth rate after 40 weeks is 1/2000 pregnancies(8). Does inducing 2000 women at 40 weeks prevent one stillbirth?  Systematic reviews say NO. Systematic Reviews of the research which were large enough to study perinatal outcomes have found no significant difference in perinatal mortality including stillbirths between induction and expectant management groups(1,9,10*, , and 11).

The studies supporting induction at 41 weeks are 3 low quality observational studies. The first is co-authored by Mary E. Hannah, author of Breech Trial, who persistently presents "data with serious concerns as far as study design, methods, and conclusions with frequent lack of adherence to the inclusion criteria."(12). Hannah’s 1999 article promoting induction for post term linked two things that may not be related: the stillbirth rates in Canada as a whole and the induction rates reported at Canadian hospitals close to where she lives, between 1980–1995(13). Perinatal mortality rates were not examined during the period. Stillbirth rates went down from 3/1000 to 2/1000.

This could have been the result of greater availability of abortion on demand, improved hospital protocols, prenatal care, nutrition, and/or less smoking or other unknowns. During the 15-year study period, induction rates increased or decreased at different rates in each place, but in general increased from 12% to 16%. Cesarean rates also increased. It is not made clear by how much; only small samples of cesarean rates at 40 and 41 weeks in the years 1986, 1992 and 1995 are given (13). Hannah’s study compares induction in one place to stillbirth rates at different places during the same time period. The studies neglect to report on perinatal mortality, and withhold known cases of babies who were permanently injured directly as a result of postdates induction protocol. (14)

The second study is by a group of five Canadian academics who chose to study American, not Canadian, birth certificate data from 1991–1997 (2). Birth certificate data is known to be unreliable. The birth certificate data used shows no indication of why labor induction was used and the authors admit the data includes inductions for an already dead fetus and for a fetus that was already compromised. Therefore, the outcomes of actual inductions involving a live fetus is unknown. Like the other studies, this study compares stillbirth rates (not perinatal mortality) to approximate induction rates during a six-year period in which induction increased from 10% to 20%.

A third study is again retrospective research using birth certificate data reporting a 1/1000 decrease in stillbirths associated with induction.(15)  Again, the data is birth certificate data. Again important variables that affect stillbirth rates are not controlled for.  This study shows that induction is associated with a significantly higher rate of problematic babies that need intensive care though no long term follow up was made to know if this results in a significantly higher rate of long term brain damage.

All 3 studies admit that it is impossible to draw conclusions or base protocol on their findings since so many factors could lower the stillbirth rate. Nevertheless, those studies are all the evidence there is to support a policy of induction at 41 weeks.

Many doctors are opposed to postdate induction protocols  "The induction of labour between 41 and 42 weeks is a very crude strategy for reducing term and post-term stillbirth rates. Although the risk of fetal death is increased after 42 weeks, many more fetuses die in utero between 37 and 42 weeks than die in the post-term period. It appears that smaller term fetuses run a far greater risk than their larger counterparts, and that current methods of antepartum assessment of the term fetus are still inadequate" (16).   Difficulty in identifying at-risk fetuses is what has led to routine inductions and better methods are needed(17).

Prenatal testing cannot predict stillbirth or perinatal mortality As much as we would like a prenatal test and subsequent intervention that would prevent postdate stillbirth, there is none. Risk screening and prenatal tests have many false positive results and the majority of adverse outcomes occur in the larger population of women identified as low-risk. "There is no effective screening test that has clearly shown a reduction in stillbirth rates in the general population"(18,19). Tests that do NOT decrease stillbirth and perinatal mortality compared to control group (19) are:
 

  • Fetal movement counting

  • Routine ultrasound scanning

  • Doppler velocimetry

  • Detection and management of maternal diabetes mellitus

  • Antenatal fetal heart rate monitoring using cardiotocography

  • Fetal biophysical profile test scoring (BPP)

  • Vibroacoustic stimulation

  • Amniotic fluid volume assessment (AFI)

  • Home vs. hospital-based bed rest and monitoring in high-risk pregnancy

  • In-hospital fetal surveillance unit

  • Use of the partograph during labor

  • Cardiotocography during labor with or without pulse oximetry

Macrosomia In addition to supposed avoidable stillbirth, another false justification for inducing labor postdates is based on the fact that the healthy fetus continues to gain weight in utero and larger babies may suffer damage on the way out. The 2011 Cochrane Review found three trials involving 372 women rigorous enough to draw conclusions. The evidence shows that induction of labor for suspected fetal macrosomia in non-diabetic women has not been shown to alter the risk of maternal or neonatal morbidity (20).

In countries with relatively low induction rates of 15% (Denmark and Sweden), where 8% of births take place ≥42 weeks, 4% of babies weigh 4500 g or more at birth. In countries like Austria and Belgium, where 40% of pregnancies are induced, only 0.5% of births take place ≥42 weeks, and 1% of babies weigh 4500 g or more at birth(1). Induction results in lower birth weights but not better newborn outcomes. 

Brachial palsy (OBPP) is palsy of the newborn’s upper arm muscles that resolves itself within the first year in about 80% of cases. (shoulderdystociainfo.com) It is caused by damage to nerves in the neck while struggling to deliver a large head in breech birth or stuck shoulders. There is no perfectly accurate way to predict birth weight and even if you could, half the cases of shoulder dystocia (21)  happen when the birth weight is less than 4000 g.

Infants delivered by caesarean section have a lower risk of brachial plexus injury but between 1 and 4% of OBPP cases accompany cesarean surgery.  500 cesarean deliveries would have to be performed to prevent one case of OBPP. More experienced practitioners have a lower incidence of OBPP because the risks may be less if there is no panic, pressure on the fundus, lateral traction or pivoting of the head at the neck or rotational movement of the head in an attempt to rotate the shoulders.

Placental insufficiency As long as the baby keeps growing, the placenta is obviously functioning well, which indicates that the fetus should be able to tolerate spontaneous labor. Where the baby is thought to have stopped or slowed down its growing, a genetic defect is suspected.

Placental dysfunction is blamed as the cause of miscarriage and stillbirth but there is no evidence to support this theory. Consecutive measurement of the height of the uterine fundus with a tape measure by the same caregiver has been shown effective at picking up the fetus that is not gaining weight. Abdominal measurements facilitate a relationship between a woman and her baby, and educate couples about nutrition, which contributes to better outcomes.

When a fetus is suspected to be small-for-dates, the antenatal care provider can focus on behavioral, social and environmental influences that could be mitigated, including smoking and poor nutrition. Induction has not been shown to improve outcomes perhaps because diagnosis of IUGR is most often wrong and real IUGR babies are probably not good candidates for the difficult labor associated with induction.

Oligohydramnios Oligohydramnios diagnosed after birth is associated with poorer outcomes, but inducing based on Amniotic Fluid Index (AFI) has never been shown to prevent poor outcomes.  Research comparing AFI in the summer and winter has proven that AFI directly reflects the amount of fluid the mother is drinking and how much she is sweating(22). 

In a 2004 study, scientists failed to find poor outcomes associated with an AFI ≤5 cm measured within seven days of delivery in the third trimester(23). They found no difference in umbilical arterial pH or base excess, even in small-for-gestational-age (SGA) infants, including those with suspected placental insufficiency. There was no difference in the number of SGA neonates, 5-minute Apgar <7, respiratory distress syndrome, necrotizing enterocolitis or neurologic morbidity from matched controls with normal AFI.

"Amniotic fluid stems from the baby’s urine, and the urine results from good blood flow, so if we see low fluid, the assumption is that there is not good blood flow and the fetus is compromised. This study shows the amniotic fluid index is not as good as we thought, and there is no reason to deliver the baby early if other tests are normal"(25).

In a prospective study of 3050 pregnancies, AFI failed to predict lack of fetal well-being and had "no prognostic significance"(24). Cochrane review found "the use of the amniotic fluid index increases the rate of diagnosis of oligohydramnios and the rate of induction of labor without improvement in peripartum outcomes"(25). A 2007 article found that single deepest pocket (SDP) measurement is as useless as AFI (26).

Meconium Aspiration Syndrome Women are told they need to be induced at 41 weeks to decrease the risk of meconium aspiration. Meconium is not the cause of meconium aspiration. A 2009 review of randomized control trials found pulmonary hypertension and asphyxia, not the presence of meconium, to be the important risk factors for MAS(27). It is likely that perinatal distress and aspiration of meconium occur earlier in the pregnancy, not at birth, which is why suctioning or cesarean delivery does not improve outcomes.

Universal intrapartum suction of infants with meconium stained amniotic fluid has proven useless. Instead, endotracheal intubation and suctioning are currently recommended only for nonvigorous infants. Respiratory failure in infants with MAS is initially treated with mechanical ventilation and surfactant administration.

Suctioning of the hypopharynx is associated with delay in onset of resuscitation, damage to the mouth and hypopharynx, and cardiac arrhythmias secondary to vagal stimulation. A 2009 study concluded, "Routine suctioning is more likely to cause harm than good and should therefore be abandoned as a routine procedure"(27).

A 2009 systematic review (1966–2007) suggests elective induction of labor ≥41 weeks is associated with a decreased risk of meconium stained amniotic fluid, but the lack of quality studies shows a lack of evidence that this translates into better outcomes. Therefore, more research is required before induction can be justified(28).

Drawbacks of Elective Induction for Post term Elective induction has been shown to increase cesarean rates by 5%(29) Elective cesarean at term has 3X the perinatal mortality of vaginal birth(30). United States statistics show a 13% increase in premature singleton births for the years 1991–2006, the increase occurring among births between 34–36 weeks, with no change in the earlier weeks of prematurity(30). During this period induced labor doubled from 8% to 16%, suggesting "that the increase in the preterm birth rate was related to increases in obstetrical interventions" without any improvement in US infant and fetal mortality rates. 

The rate of amniotic fluid embolism (AFE) is increasing from previous rates of 1/120,000 and occurred in 1/50,000 births from 2005–07 in the United Kingdom(31). Among the 60 cases of AFE reported, half were labor inductions. A 2010 Australian study found the same recent increase in AFE associated with induction (32). Consider this case, of a typical, routine induction: a 40-year-old woman with an unremarkable obstetric or medical history admitted at 41+ weeks for induction due to reduced fetal movement; fetal head down; estimated fetal weight 3600g; cervix not effaced or dilated.

The woman was induced with three prostaglandin E (PGE) doses over 16 hours. Epidural analgesia was administered. At 7 cm membranes were artificially ruptured. Ten minutes later the cervix was fully dilated and the patient started pushing. Respiratory distress appeared and the patient was ventilated and intubated, then died of amniotic fluid embolism (33). 

Resources 1. Zeitlin J., B. Blondel, S. Alexander, et al. 2007. "Variation in rates of post term birth in Europe: reality or artifact?" BJOG 114:1097–103.

2. Yuan H., R.W. Platt, L. Morin, et al. 2005. "Fetal deaths in the United States 1997 vs 1991." Am J Obstet Gynecol 193:489–95.

3. Laughon SK, Zhang J, Grewal J, Sundaram R, Beaver J, Reddy UM. Induction of labor in a contemporary obstetric cohort. Am J Obstet Gynecol. 2012;206(6):486.e1-9.

4. Sladkevicius P., S. Saltvedt, H. Almström, et al. 2005. "Ultrasound dating at 12–14 weeks of gestation. A prospective cross-validation of established dating formulae in in-vitro fertilized pregnancies." Ultrasound Obstet Gynecol 26 (5): 504–11.

5. Lynch C.D., and J. Zhang 2007. "The research implications of the selection of a gestational age estimation method." Paediatr Perinat Epidemiol 21 Suppl 2:86–96.

6. Roos N, L. Sahlin, G. Ekman-Ordeberg, et al. 2010."Maternal risk factors for post term pregnancy and cesarean delivery following labor induction." Acta Obstet Gynecol Scand 89 (8): 1003–10.

7. Taipale P., and V. Hiilesmaa. 2001. "Predicting delivery date by ultrasound and last menstrual period in early gestation." Obstet Gynecol 97:189–94.

8. Smith G.C., J.P. Pell, and R. Dobbie. 2003. "Caesarean section and risk of unexplained stillbirth in subsequent pregnancy." Lancet 362 (9398): 1779-84.

9. Sanchez-Ramos L, Olivier F, Delke I, Kaunitz AM. Labor induction versus expectant management for postterm pregnancies: a systematic review with meta-analysis. Obstet Gynecol 2003;101:1312–18.

10. Gülmezoglu AM, Crowther CA, Middleton P. Induction of labour for improving birth outcomes for women at or beyond term. Cochrane Database of Systematic Reviews 2006, Issue 4. Art. No.: CD004945. DOI: 10.1002/14651858.CD004945.pub2

* Found increase in perinatal mortality in the non-induced group, but "the absolute difference was extremely small" and half the patients in the review were from a 1992 study by Mary Hannah, whose reputation precedes her, in which labor was not induced until 44 weeks. "The cause of the deaths was possibly not related to pregnancy duration in some of the cases." according to: Greve T et.al.Maternal and perinatal complications by day of gestation after spontaneous labor at 40-42 weeks of gestation.Acta Obstet Gynecol Scand. 2011;90(8):852-6.

11.Wennerholm UB, Hagberg H, Brorsson B, Bergh C. Induction of labor versus expectant management for post-date pregnancy: is there sufficient evidence for a change in clinical practice? Acta Obstet Gynecol Scand. 2009;88(1):6-17.

12. Glezerman, M. 2006. "Five years to the term breech trial: the rise and fall of a randomized controlled trial." Am J Obstet Gynecol. 194 (1): 20–5.

13. Sue-A-Quan, A.K.. M.E. Hannah, M.M. Cohen, et al. 1999. "Effect of labour induction on rates of stillbirth and cesarean section in post-term pregnancies." CMAJ 160:1145–9.

14. Menticoglou SM, Hall PF. Routine induction of labour at 41 weeks gestation: nonsensus consensus. BJOG. 2002;109(5):485-91.

15. Stock SJ, Ferguson E, Duffy A, Ford I, Chalmers J, Norman JE. Outcomes of elective induction of labour compared with expectant management: population based study. BMJ. 2012 (May10);344:e2838.

16. Hollis B. 2002. "Prolonged pregnancy." Curr Opin Obstet Gynecol. 14 (2):203–7.

15. Ahmed A.I., and E. Versi. 1993. "Prolonged pregnancy." Curr Opin Obstet Gynecol 5 (5): 669–74.

18. Smith G.C. and R.C. Fretts. 2007. "Stillbirth." Lancet 370 (9600): 1715–25.

19. Haws RA, Yakoob MY, Soomro T, Menezes EV, Darmstadt GL, Bhutta ZA. Reducing stillbirths: screening and monitoring during pregnancy and labour.BMC Pregnancy Childbirth. 2009;9 Suppl 1:S5. Review.

http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2679411/pdf/1471-2393-9-S1-S5.pdf

20. Irion, O., and M. Boulvain. 2000. "Induction of labour for suspected fetal macrosomia." Cochrane Database Syst RevCD000938.45.

21. Doumouchtsis, S.K., and S. Arulkumaran. 2010. "Is it possible to reduce obstetrical brachial plexus palsy by optimal management of shoulder dystocia?" Ann N Y Acad Sci 1205 (1):135–43.

22. Feldman I., M. Friger, A. Wiznitzer, et al. 2009. "Is oligohydramnios more common during the summer season?" Arch Gynecol Obstet 280 (1): 3–6.

23. Driggers. R.W., C.J. Holcroft, K.J. Blakemore, and E.M. Graham. 2004 "An amniotic fluid index < or =5 cm within 7 days of delivery in the third trimester is not associated with decreasing umbilical arterial pH and base excess." J Perinatol 24 (2): 72–6.

24. Locatelli A., A. Zagarella, L. Toso, et al. 2004. "Serial assessment of amniotic fluid index in uncomplicated term pregnancies: prognostic value of amniotic fluid reduction." J Matern Fetal Neonatal Med 15 (4): 233–6.

25. Nabhan A.F., and Y.A. Abdelmoula. 2008. "Amniotic fluid index versus single deepest vertical pocket as a screening test for preventing adverse pregnancy outcome." Cochrane Database Syst Rev 3:CD006593.

26. Magann, E.F., S.P. Chauhan, D.A. Doherty, et al. 2007. "The evidence for abandoning the amniotic fluid index in favor of the single deepest pocket." Am J Perinatol 9:549–55. http://www.ncbi.nlm.nih.gov/pubmed/17909990.

27. Vain N.E., E.G. Szyld, L.M. Prudent, et al. "What (not) to do at and after delivery? Prevention and management of meconium aspiration syndrome." Early Hum Dev 85 (10): 621–6.

28. Caughey A.B., V. Sundaram, A.J. Kaimal, et al. 2009. "Maternal and neonatal outcomes of elective induction of labor." Evid Rep Technol Assess (Full Rep) 176:1–257.

29. Lowe N.K. 2007. "A review of factors associated with dystocia and cesarean section in nulliparous women." Journal of Midwifery & Women’s Health 52 (3): 216–28.

30. MacDorman M.F., E. Declercq, and J. Zhang. 2010."Obstetrical intervention and the singleton preterm birth rate in the United States from 1991-2006." Am J Public Health 100 (11): 2241–7.

31. Knight M., D. Tuffnell, P. Brocklehurst, et al. 2010. UK Obstetric Surveillance System. "Incidence and risk factors for amniotic-fluid embolism." Obstet Gynecol 115 (5): 910–7.

32. Roberts C., C. Algert, M. Knight, et al. 2010. "Amniotic fluid embolism in an Australian population-based cohort." BJOG 117 (11): 1417–21.

33. Chanimov M., I. Ben-Shlomo, B. Chayen, et al. 2008. "Amniotic fluid embolism: a plea for better brain protection." Isr Med Assoc J 10 (2): 154–5.

Judy Slome Cohain is a masters degree certified nurse midwife in the US who has been living and working in Israel since 1983 as an unlicensed midwife. This twist of fate enables her to practice evidence-based midwifery, instead of less-than-optimal protocols to protect a license. Judy welcomes feedback or questions which can be sent to  judyslome@hotmail.com