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Friedman's Curve

Adapted from Report on Friedman's Curve 2013, by Rebecca Dekker

Friedman’s Curve and Failure to Progress: A Leading Cause of Unplanned C-sections


© August 28, 2013 by Rebecca Dekker, PhD, RN, APRN of www.EvidenceBasedBirth.com


“Failure to progress” is the number one reason for unplanned C-sections in the U.S.


In 2013, researchers published a report of 38,484 first-time C-sections that occurred among a national sample of women. 


The overall C-section rate among first-time mothers was 30.8%. 


More than 1 in 3 (35%) of these Cesareans were due to a diagnosis of “failure to progress,” or slow progress in labor. 


This means that 10%, or 1 in 10, of all first-time mothers in the U.S. had a Cesarean for failure to progress during the years 2002-2008 *


More than 4 in 10 of these women who had C-sections for failure to progress had not even reached 5 cm dilation before they were taken to surgery. This means that many of these women were still in very early labor when they were told that they weren’t dilating fast enough.* 


Out of women who reach the pushing phase, 1 out of 3 of cesarean deliveries for failure to progress during pushing were performed at less than 3 hours of pushing in first-time mothers, while 1 out of 4 C-sections for failure to progress during pushing were performed at less than 2 hours in experienced mothers. 


This is of concern because the 2003 ACOG guidelines define “arrest of descent” as greater than 3 hours in first-time mothers with epidurals and greater than 2 hours in experienced mothers with epidurals, and the majority of American women have epidurals during labor– which can lead to a slower pushing phase (Zhang et al. 2010b).

A substantial number of women have unplanned Cesareans for failure to progress during a medical induction. In a 2010 study that included 233,844 newborns born between 2002 and 2008, researchers found that about half of all induced women who had C-sections for failure to progress had not reached 6 cm yet (53%)– indicating that they were still in very early labor when their inductions were labeled as “failed” (Zhang et al., 2010b).


Why do so many women have unplanned Cesareans for failure to progress?

 “Friedman’s Curve” is a graph that obstetricians have traditionally used to define a “normal” length and pace of labor - If a woman’s cervix does not dilate according to this schedule, she may be assigned a diagnosis of “failure to progress” and taken  for a Cesarean.


So what is this Friedman’s curve? When was it invented? Does it apply to women today?

In 1955, Dr. Friedman of Columbia University published a study describing the average amount of time it took women to dilate during labor (Friedman 1955). Until then, doctors had simply published research studies that described the total length of labor. Dr. Friedman went one step further by plotting women’s labors on a graph, and then figuring out the average length of time it took to a woman to dilate each centimeter. This graph became known as the famous “Friedman’s Curve.” .

Although it was published nearly 60 years ago, Friedman’s curve still serves as the basis of how most physicians define normal labor. In fact, as recently as 2010, researchers claimed that Friedman’s curve continues to “govern labor management.” In other words, most care providers use this graph to dictate how they manage a woman’s labor 


So who were the women in the famous Friedman’s Curve?

Dr. Friedman’s study focused on 500 first-time mothers who gave birth at term in 1954. These women ranged in age from 13-42 years old, and the average age was 20 years old. More than half of the women had forceps used on them during the delivery (55%), and only 9 women (1.8%) gave birth by C-section. There were 14 breech births (2.8%), 4 twin births (.9%), and 4 stillbirths or neonatal deaths. The babies ranged in weight from 4 lb 9 oz to 10 lb 6 oz, with most babies falling into a normal weight range (5 lbs 8 oz to 8 lbs 13 oz). Pitocin was used to induce or augment labor in 13.8% of women.  23% of the women were lightly sedated, 42% were moderately sedated, and 31% were deeply sedated (sometimes “excessively” sedated) with Demerol and scopolamine—meaning that 96% of the women were sedated with drugs.

Dr. Friedman found that the average length of time it took these first-time mothers to get from 0 cm to 4 cm was 8.6 hours (± 6 hours). The average length of the time it took to get from 4 to 10 cm was 4.9 hours (± 4 hours). The average length of pushing (second stage) was 1 hour (± 0.8 hours). Once women hit 4 cm, their labors sped up—meaning that they hit “active labor”—and they dilated on average 3 cm per hour (± 2 cm) until they reached 9 cm, after which there was a slight slowing down between 9 cm and 10 cm.

The Friedman curve study was important at the time because it described labor in a way that had never been done before. However, modern researchers have come to the definitive conclusion that we can no longer apply Friedman’s curve to women of today’s world. Too many things have changed since 1955. Women are no longer sedated during labor, but epidurals are commonplace; Pitocin is used much more frequently for both labor induction and augmentation, women are older and tend to weigh more, and forceps are hardly ever used. All of these things can either slow down or speed up the rate of labor.


Factors that may lengthen or shorten labor:

May lengthen labor:

Epidural use may lengthen both labor (Alexander et al. 2002, Frigo et al. 2011) and pushing (Anim-Somuah et al. 2011)

Heavy sedation (Friedman 1955)

Being overweight or obese (Kominiarek et al. 2011)

Older maternal age (Sheiner et al. 2002a)

Medical labor induction (Sheiner et al. 2002a) (Vahratian et al. 2005)

Giving birth for the first time (“)  (Zhang, Landy et al. 2010) Posterior positioning of the baby (sunny-side up) (Gardberg & Tuppurainen 1994, Senecal et al. 2005)

Being confined to a bed (Lawrence et al. 2013)

A lower rate of IV fluids  (Note: when women are allowed to drink freely, their labors are, on average, the same length as women who are given IV fluids

Having been a victim of sexual assault (Nerum et al. 2010)

Being pregnant with twins (Leftwich et al. 2013)

Premature rupture of the membranes  (Sheiner et al. 2002a)

Being pregnant with a big baby (Sheiner et al. 2002b)

Maternal complications including: gestational diabetes, hypertension or preeclampsia, low fluid or high fluid levels, having had a previous infant die during or shortly after labor, and infertility treatment


May shorten labor:

Pitocin augmentation/acceleration (Bugg et al. 2013)

Having given birth before (Zhang, Landy et al. 2010; Sheiner et al2002a)

Upright positions— during labor and pushing (Gupta et al. 2012)


May lengthen or shorten labor, or may not change anything at all:

Artificially breaking the waters (Friedman 1955; Smyth et al. 2013)


For women who go into labor on their own, labors tend to be much slower today than they were in 1955. In an important study that took place in 2010, researchers looked at the labor records of more than 62,000 women from 19 hospitals across the U.S. The women were included if they gave birth vaginally at term to a single baby who was positioned head-down, if the babies were born healthy, and if the mothers went into labor on their own (not induced). Overall, about half the mothers had their labors “augmented” or sped up with oxytocin (Pitocin), and 80% had epidurals (Zhang, Landy et al. 2010).The researchers found that on average, mothers did not rapidly dilate starting at 3 cm like Dr. Friedman saw back in 1955. Instead, women began to see active labor at 6 cm. This was true for both first-time mothers and experienced mothers, although experienced mothers tend to dilate faster once they hit active labor (6 cm). The average time it took to dilate during active labor was about half an hour for each centimeter (but it was faster for experienced mothers). The majority of women (95%)  took less than 2 hours to dilate 1 centimeter during active labor.

Interestingly, researchers found that many women went long periods without any dilation—and this was normal for them. Women took on average 1.8 hours to get from 3 to 4 cm, and 1.3 hours to get from 4-5 cm, And some women (the top 5%)—both first-time mpthers and experienced mothers—took as long as 8 hours to get from 3 to 4 cm, while others took as long as 7 hours to dilate from 4 to 5 cm (See more information here). All these women went on to give birth vaginally to healthy babies.

When it came to pushing, or the “second stage” of labor, first-time mothers pushed for an average of 1.1 hours with an epidural and 0.6 hours without an epidural. At the very extreme end of normal, some first-time mothers (top 5th percentile) pushed for 3.6 hours with an epidural and 2.8 hours without an epidural. Experienced mothers had much shorter pushing phases—on average, they spent less than 30 min pushing with an epidural, and about 15 minutes without an epidural.

Other researchers have also confirmed that modern women have slower labors than they did in Dr. Friedman’s time. In 2010, researchers combined the results of 18 studies from 1990-2008 that reported the average length of labor among 7,009 first-time mothers who went into labor on their own (not induced). In these studies, “active labor” was defined as having contractions and being at least 3-5 centimeters dilated. A large number of women in these studies received Pitocin augmentation, artificial rupture of membranes, and epidurals for pain relief (Neal et al. 2010).

Researchers found that among all of these modern first-time mothers, the average length of active labor (after reaching 3-5 cm) was 6 hours, with women dilating on average 1.2 cm per hour during the active stage. These results were quite different from what Friedman found more than half a century ago. In 1955, Friedman described 1.2 cm per hour as the “lowest acceptable rate” of cervical dilation. But among modern women, 1.2 cm per hour was actually the AVERAGE rate of dilation. Half of women dilated slower than 1.2 cm per hour, and half dilated faster than this. In other words, what was considered “slow labor” in Dr. Friedman’s day is actually the normal rate of dilation today.


So here lies the problem. If we continue to use the Friedman Curve, we are saying that half of all women have abnormally slow labors. This means that there is something very wrong with our definition of abnormal. We expect first-time mothers to dilate much faster than average, and we expect them to have much shorter labors than they naturally do. As a result, many women are being incorrectly diagnosed with failure to progress, when what they are experiencing is actually normal, and could be more aptly named “failure to wait.”


But is it harmful for women to have long labors? What are the risks to mothers and babies?


There does not appear to be any difference in infant mortality if a woman has a longer labor, although babies may have lower Apgar scores and there may be a higher risk of blood loss in the mother. From 1988-1999, Israeli researchers looked at more than 94,000 women who gave birth and compared the 1.3% of women who were diagnosed with failure to progress (with Friedman’s curve) to everyone else who had normal-length labors. (Interestingly, rates of failure to progress seen in this study were much lower than what is seen in the U.S.)

There were no differences in mortality rates between babies who were born after a prolonged labor and those who were not. However, babies born to women who had failure to progress were more likely to have Apgar scores <7 at 5 minutes after birth (1.3% vs. 0.2%). Mothers who were diagnosed with failure to progress during the first stage were more likely to be anemic after the birth (47% vs. 23%) and need a blood transfusion (5.6% vs. 1%) (Sheiner et al. 2002a).

On the other hand, in a study of more than 10,000 first-time mothers that took place between 1990-2008 in the U.S., (Cheng 2010) babies who were born after a first stage of labor that took longer than 30 hours were more likely to be admitted to the neonatal intensive care unit (9.8% vs. 4.7%), but there was no other relationship between long labors and other poor newborn outcomes—including Apgar scores, umbilical cord pH, meconium aspiration, newborn infection, shoulder dystocia, or birth trauma. Women who had longer labors were more likely to have an infection of the uterus (23.5% vs. 12.5%) and have a C-section (13.5% vs. 6.1%), but there was no increase in the risk of postpartum hemorrhage. The authors did not describe the number of vaginal exams women received, which was important, because a larger number of vaginal exams could have contributed to higher infection rates among the women with long labors (Cheng et al. 2010).


What are the risks of pushing for longer periods of time?

In 2006, researchers reviewed 8 studies that were conducted between 1980 and 2005 and looked at the relationship between length of pushing and mother-baby outcomes. They found a strong relationship between a longer pushing phase and a higher rate forceps or vacuum use and C-sections.  Four out of 5 studies found that women with longer pushing phases were more likely to have postpartum hemorrhage, and three out of 5 studies found a higher rate of postpartum infection among women who pushed for more than 2 hours (Altman et al. 2006).

When it came to health outcomes for the baby, none of the studies in the review found a relationship between longer pushing phases and lower Apgar scores, umbilical cord pH, seizures, need for ventilation support, or death. Only 1 of 8 studies found that newborns had a higher rate of NICU admissions after a pushing phase that exceeded 2 hours.

Since the publication of the 2006 review article, 2 more researchers have looked at the relationship between length of pushing and mother/baby outcomes. In 2007, Cheng et al. specifically looked at the records of experienced mothers who had pushed for longer than 3 hours between the years 1991 and 2001. They found that experienced mothers who pushed for more than 3 hours had higher rates of vacuum and forceps delivery, C-section, 3rd and 4th degree tears, postpartum hemorrhage, and infection. Their newborns had higher risks of low Apgar scores, meconium in the broken water, admission to the NICU, and a longer hospital stay.

Then in 2009, researchers looked at the health records of 121,517 low-risk women who gave birth in Nova Scotia between 1988 and 2006. About half of these women were first-time mothers. Fifteen percent of the first-time mothers pushed for more than 3 hours, and 3% of experienced mothers pushed for more than 2 hours. Almost all of the women with prolonged pushing phases had epidurals (Allen et al. 2009).

The researchers found that first-time mothers who pushed for more than 2 hours and experienced mothers who pushed for more than 1 hour were more likely to have chorioamnionitis, obstetric trauma (including 3rd or 4th degree tears), postpartum hemorrhage, wound complications, and fever—even after taking into account other factors such as epidural and antibiotic use. The increased risk of chorioamnionitis among first-time mothers appeared to mostly be due to C-sections. There was no increased risk of blood transfusion and wound complications among first-time mothers with longer pushing phases. However, the risks of blood transfusion and wound complications risks did increase among experienced mothers with longer pushing phases.

When researchers looked at newborn health outcomes, babies born to women who pushed longer than 2 hours (both first-time mothers and experienced mothers) were more likely to have lower Apgar scores, minor birth trauma, and NICU admissions. There was no increase in the risk of infection (sepsis) or major birth trauma.

Although some of these increased risks seem ominous, most of the increased risks (odds ratios) were actually small increases in risk, and the researchers pointed out that the risks did not seem to rise substantially until pushing phases were longer than 3 hours in first-time mothers and 2 hours in experienced mothers. 


What are the evidence-based definitions of normal and abnormal?

Because of all of the updated research evidence in the past 10 years, the proposed definitions of normal and abnormal length of labor look quite different than the old definitions. The American Congress of Obstetricians and Gynecologists (ACOG) have not updated their guidelines on slow labor since 2003.  But in 2012, ACOG, the Society for Maternal Fetal Medicine, and the National Institute for Maternal and Child Health came together in a joint workshop and issued new definitions of normal labor and arrested labor   (SEE DEFINITIONS)


What about failed induction of labor? How is it diagnosed?

This is an important question, because in modern times in the U.S., more than 4 out of 10 first-time mothers have their labor medically induced. At least one-third of these inductions have no medical indication. First-time mothers who are induced at term for no medical reason have a C-section rate of approximately 24%, with the largest percentage of these Cesareans being performed in early labor—before the woman reaches 6 cm (Laughon et al. 2012).


In ACOG’s guidelines on elective induction, they state that women should be “allowed” at least 12-18 hours of latent (early) labor before diagnosis of a failed induction. But in the joint workshop sponsored by ACOG, the Society for Maternal Fetal Medicine, and the National Institute for Maternal and Child Health, a new definition was proposed—and this one gives women at least 24 hours of oxytocin (Pitocin) and water breaking before a failed induction can be diagnosed (and this clock starts after cervical ripening is performed, if necessary) (Spong et al. 2012).

Recent evidence supports giving women a longer period of time during an induction before diagnosing the induction as “failed.” In 2011, researchers (Rouse et al. 2011) looked at women who had taken part in a clinical trial testing fetal pulse oximetry. To be included in this secondary study, women had to be first-time mothers, be induced with oxytoxcin, and have an unripe cervix (n = 1,347). Nearly all of the women (98%) had epidurals. The 1,219 women who started the induction with their water intact received Pitocin for on average 3 hours before their water broke, and the total length of the induction was about 16.5 hours (ranging from 4 to 123 hours). Once women received Pitocin and had their water broken, it took about 6 hours for 70% of women to reach active labor (active labor was defined as 5 cm and any effacement or 4 cm and 90% effaced).  

Although the risk of a C-section went up the longer an induced woman stayed in early (latent) labor, nearly 40% of women who had an early labor that lasted more than 12 hours still went on to have a vaginal delivery. Women with longer early phases were more likely to have chorioamnionitis or endometritis (31% for those with early labors (Pitocin + ruptured membranes) that lasted more than 12 hours versus 16% for those with early labors less than 6 hours).  Although the researchers said that they recorded the exact time of each cervical exam, they did not report the number of vaginal exams in the article. This makes it hard to determine whether the higher infection rates in women with longer labors was due to the longer time itself or an increased number of vaginal exams. Women with longer early phases of labor also had higher rates of uterine atony (11.3% vs. 5.7%), a condition when the uterus stops contracting and gets ”boggy” after birth—which can lead to postpartum hemorrhage, but there were no significant differences in perineal tears, blood transfusions, NICU admissions, or any other newborn outcomes (Rouse et al., 2011).


Other studies have found that there are no harmful effects to the baby if a woman is given more time to labor with an induction. Researchers have shown that women who are induced are more likely to have longer early labors than women who go into labor on their own (Harper et al. 2012). There doesn’t seem to be any problem with giving mother and baby some more time to reach active labor, as long as both are doing well. In 3 studies in which researchers examined long inductions and infant outcomes, there was no link between a longer early phase of labor (up to 12-18 hours) during an induction and newborn outcomes (Rouse et al. 2000, Simon and Grobman 2005, Rouse et al. 2011).


Is there anything that can increase a woman’s risk of being diagnosed with a failed induction?

Evidence shows that having an unripe cervix at the time of your induction and the way your hospital and individual care provider practice may all increase your risk of ending up with a failed induction and Cesarean.

Having an unripe cervix: In one study, researchers compared 143 first-time mothers who were electively induced with an unripe cervix, 286 first-time mothers electively induced with a ripe cervix, and 1,771 first-time mothers who went into labor on their own. All of the inductions were done with Pitocin, and the women with unripe cervixes had their cervixes ripened using the Foley bulb method.

The researchers found that women who had an unripe cervix and were electively induced were 3 ? times more likely to have a C-section compared to those women who went into labor on their own. The women who did not have a ripe cervix when they were induced also had a much slower labor compared to women who were induced with a ripe cervix (Vahratian et al. 2005).

The hospital you choose: The percentage of first-time mothers who ended up with C-sections for failed inductions ranged from 27%-55% for elective inductions and 35-56% for medically-necessary inductions. This means that different hospitals use very different criteria to diagnose a failed induction, and a woman may end up at a hospital with care providers who are significantly more likely to “diagnose” a failed induction (Teixeira et al. 2013).

The individual care provider you choose:  Another research study found that there is a “physician” effect when it comes to the risk of C-section with elective induction. At a large city hospital in the U.S., researchers looked at all of the first-time mothers who gave birth to head-down, single babies over a 2 year period. When they looked at all the different risk factors for C-sections in these women, the individual physician was one of the strongest predictor of whether or not an elective induction would turn into an unplanned C-section.  On average, elective induction doubled the risk of unplanned Cesarean in first-time mothers, but that risk could be much higher or lower, depending on whom the woman’s physician was (no midwives were included in this study) (Luthy et al. 2004).

Could changing the definition of the speed of normal dilation help prevent preventable Cesareans?

In their joint workshop, the National Institute of Child Health and Human Development, the Society for Maternal-Fetal Medicine, and ACOG came together to discuss ways to “Prevent the First Cesarean.” In their summary statement, they came to the conclusion that reducing the number of diagnoses of “failure to progress” would help prevent a large number of first-time C-sections (Spong et al. 2012).


Importantly, the workshop attendees declared that non-medical factors play an important role in C-sections that are performed for failure to progress. Time constraints, labor and delivery scheduling issues, operating room staff availability, and limited space and resources to support long labors and inductions are all factors that encourage providers to mislabel a woman’s labor as “failure to progress.” Other factors that lead to an overabundance of failure to progress diagnoses include care provider fatigue, high work load, and sleep deprivation. In fact, evidence has shown that C-section rates for failure to progress go up when the care provider knows that they can go to sleep, or go to the clinic to see patients after the delivery (Klasko et al. 1995, Spetz et al. 2001, Spong et al. 2012).

The workshop summary also stated that there are financial incentives to diagnose failure to progress. Cutting a long labor short by taking a woman to the operating room is time-efficient—this way, care providers and other staff can turn their attention to other laboring women. Multiple diagnoses of failure to progress can bring in more money to a hospital when more and more women are told to have C-sections because their cervix won’t dilate. At the same time, a long labor may prevent a care provider from seeing additional clients in the clinic. Overall, since it takes so long to monitor a woman with a longer labor, there are strong financial incentives for both the care provider and hospital staff to give up on her (“abandon” the labor) and recommend a Cesarean instead.

To stop the flood of over-diagnoses of “failure to progress,” the following recommendations were made at the workshop:

Care providers should stick to proper definitions of labor arrest, and avoid using the vague term “failure to progress” 

Women should be given adequate time for labor and pushing—and an “adequate” time is much longer than what has traditionally been allowed in the past

Inductions should only be labeled “failed” after at least 24 hours of Pitocin (plus water broken, if possible)—this clock should not start until after cervical ripening is completed, if needed

Women—particularly first-time mothers—with an unripe cervix should not be induced unless the delivery is medically necessary

Each care provider should receive quality control feedback on how often they improperly diagnose labor arrest or “failed induction”


If someone is diagnosed with failure to progress, are there any other options beside C-section?

First of all, it is important that the proper definitions for “labor arrest” are used. Evidence suggests that if a woman is in normal labor (not induced), is less than 6 cm and her labor has stalled, then this is not true “labor arrest” and she should simply receive supportive care. Supportive care may mean continued observation, Pitocin augmentation if indicated, or being discharged from the hospital (discharge may occur if labor has stopped, water is intact, and mother and baby are both in good condition.) If first-stage labor arrest is diagnosed after the mother has reached at least 6 cm, medical options include breaking the water, Pitocin augmentation, and/or allowing the woman to continue to labor, as long as both mother and baby are healthy (Spong et al., 2013; Shields et al., 2007). Obviously, there will be cases of labor arrest where a Cesarean becomes necessary.  


Based on a thorough review of the evidence, Goer and Romano suggested using 4 preventive “P’s” to deal with some outside factors that may cause labor to slow down in the first place (Goer and Romano 2012). These “P’s” include:


Permission: Give women permission to move about, eat and drink when they want to, and use whatever positions they find comfortable. Natural behaviors should not be restricted unless there is a compelling medical need to do so, and unless the woman has given true informed consent for the restriction.

Physical environment: The birthing space should be large enough for the woman and her companions. There should be safe and private places to walk, tubs and showers for water therapy, and birth balls and other props that encourage upright positioning. The woman should have a say in the physical aspects of her environment, including lighting, sound, and the people who come in and out of the room.

Practices: Practices that restrict mobility—such as being tethered to continuous electronic fetal monitoring or IV fluids—should not be used unless medically necessary. If these practices become necessary, care providers should try to lessen their impact on the woman’s mobility. For example—portable electronic monitors could be used to allow the woman to walk, instead of lying in bed.

People: Care providers should be supportive, give the woman control, provide hands-on comfort measures, give reassurance and guidance, and respect her needs for privacy and dignity. Care providers should be accommodating and non-judgmental so that the woman can feel free to express her emotions without fear of being judged or being pressured to conform to staff expectations.


So what’s the bottom line?

The definition of a “normal” length of labor that is currently used by most healthcare providers is obsolete. The new, evidence-based definitions of normal labor, labor arrest, and failed induction should be adopted immediately. As long as mother and baby are both healthy, and as long as the length of labor does not qualify as an arrested labor, laboring women should be treated as if they are progressing normally. Women who are being medically induced should be given more time to complete the early phase of labor. Importantly, six centimeters should be considered the start of the active phase—not four centimeters—and caregivers should keep in mind that normal early labor (before 6 cm) sometimes includes a period in which there is no change in dilation for hours.

If more care providers begin using evidence-based definitions of  labor arrest and failed induction, we will begin to see fewer of these diagnoses, and a simultaneous lowering of the Cesarean rate.


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