A companion article to the EBB Signature Article, Evidence on: Failure to Progress.

Is it safe to have a prolonged second stage of labor? In this article, I will summarize the research evidence that specifically looks at the benefits and risks of a prolonged second stage of labor, also referred to as a prolonged pushing phase.

Background on Prolonged Second Stage of Labor

In the past, a prolonged pushing phase was defined as pushing for >3 hours in first-time mothers with an epidural, >2 hours in first-time mothers without an epidural, >2 hours in experienced mothers with an epidural, and > 1 hour in experienced mothers without an epidural (ACOG, 2003). However, recent guidelines encourage giving mothers more time to push—at least 1 additional hour for each category (ACOG, 2014).

To collect the research on the length of pushing, I performed a systematic search on PubMed, using the key terms “failure to progress AND labor or childbirth or Cesarean,” “dystocia AND labor or childbirth or Cesarean,” “labor arrest AND childbirth or Cesarean,” and “second stage of labor AND childbirth or Cesarean.” Articles were included if they reported data on the potential benefits and harms related to the length of the second stages of labor, and if they were published between 2006 and 2017. We found one randomized trial, two systematic reviews on observational evidence, and eight observational studies that fit these criteria. Note: In this article, we refer to people giving birth for the first time as first-time mothers and people who have given birth before as experienced mothers. We will specify when a study is referring only to people who have given birth vaginally before. Also, this article does not cover the evidence on “delayed pushing” in people with epidurals —whether or not they were resting at 10 cm for a while before they started pushing. If you want to learn more about delayed pushing, we recommend this article at Science & Sensibility here!

Randomized Controlled Trial

In 2016, Gimovsky and Berghella carried out the first randomized trial on the length of the pushing stage. This was a small study (78 women) that took place in 2014 to 2015 at a single hospital in Pennsylvania. Participants could be in this trial if they were having their first baby (single baby, head-first position at term), and if they had normal fetal heart monitor results during labor. If they reached the 3-hour pushing phase mark with an epidural, they were randomly assigned (like flipping a coin) to either an “extended care” group (41 women) or a “usual care” group (37 women). Women in the extended care group were given the option of continuing pushing for one additional hour, in line with the new ACOG/SMFM guidelines. Women in the usual care group were given no additional time to push. In both groups, when a woman’s time was up, she gave birth with the option of Cesarean, vacuum, or forceps. It’s important to note that this study only included women with epidurals. Women without epidurals all either gave birth before 3 hours or declined to be in the study. Those who were included, then, all had medically managed labor and births: all of the women had epidurals, about half of the women were induced (43%-54%), and most women had labor augmented with Pitocin (81%-83%). Most women (81-83%) were also instructed to delay pushing for about an hour because they did not have an immediate urge to push. This delay was included in the total time women were given for the pushing phase. Typical practice in this hospital was to instruct laboring people to hold their breath while pushing, and most people pushed while lying on their backs (93%-97%). There was a low crossover rate between groups. Two women who were assigned to the extended group received usual care, and nine women in the usual care group had extended care. The researchers found that women in the extended-time pushing group had a much lower Cesarean rate than women in the usual care group—19.5% vs. 43.2%. The researchers estimated that for every four women who received an additional hour during pushing, one woman would avoid a Cesarean. Rates of spontaneous vaginal birth (giving birth without the help of surgery, vacuum, or forceps) were also much higher in the extended care group (51.2% vs. 18.9%). The study was too small to tell differences in postpartum hemorrhage, maternal infection, severe tears, and NICU admissions—however, NICU admission rates were high in both groups (32% and 38%). According to the author, the reason the overall NICU rates were high is because this particular hospital admits every baby to the NICU whose mother had suspected chorioamnionitis (personal communication, Dr. Gimovsky, July 2016). Although the definition of suspected chorioamnionitis was not clarified, it could mean that any mother with a temperature above a certain number could be seen as having suspected chorioamnionitis (even if the fever simply related to having an epidural—a common side effect of epidurals). This study also had higher-than-normal rates of 3rd and 4th degree tears (ranging from 3% to 14%), and chorioamnionitis (27% to 35%), but with no statistical differences between groups. There were zero cases of newborn blood infections, seizures, or deaths.

Systematic Reviews of Observational Studies

In 2006, Altman et al. reviewed 8 studies that were carried out between 1980 and 2005 and looked at length of pushing and mother-baby outcomes. They found a strong relationship between a longer pushing phase and a higher rate of instrumental delivery, defined as the use of forceps, vacuum, or Cesareans. Four out of five studies found that people with longer pushing phases were more likely to have postpartum hemorrhage, and three out of five studies found a higher rate of postpartum infection among people who pushed for more than two hours. When it came to health outcomes for the baby, zero 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. Seven out of eight studies found no increase in the rate of NICU admissions after a pushing phase that exceeded two hours. Gimovsky et al. recently conducted a systematic review of prolonged second stage in first-time mothers with epidurals. They only found two studies that looked specifically at the length of pushing in first-time mothers with epidurals—a study published by Menticoglou in 1995 and a study by Laughon et al. in 2014. When they combined the results of these two studies, they found that 19.8% of first-time mothers who push for more than 3 hours will have a Cesarean, 21.6% will have a vacuum- or forceps-assisted birth, and the majority (58.9%) will have a spontaneous vaginal birth.

Observational Studies

Since the publication of the 2006 review article, eight more research teams have carried out observational studies on the relationship between length of pushing and mother-baby outcomes. To avoid making this section too long, we will summarize the findings of each study, and share detailed statistics from the largest, most recent study in the U.S. (Laughon et al. 2014). We will begin with the two studies that included only first-time mothers, followed by the one study that included only experienced mothers, and then describe the rest of the studies that included both. A shorter description of these studies is available in Table 3.

Prolonged Pushing Phases in Sweden

In 2015, Altman et al. used Swedish medical birth records from 2008 to 2012 to determine if longer second stages are related to low Apgar scores. There were nearly 33,000 first-time mothers in this study, and people could be included in the study if they gave birth to a live, singleton child at term in head-first position. They excluded people with elective Cesareans or who had medical labor inductions. Participants were divided into five groups based on the length of the second stage: <1 hour, 1 to <2 hours, 2 to <3 hours, 3 to <4 hours, and 4 hours. Overall, only 0.7% of the infants had a 5-minute Apgar score of <7, and 0.1% had a 5-minute Apgar score of <4. The researchers found that although low Apgar scores at 5 minutes were rare, they happened more often in people who had longer second stages of labor, even after taking into account the person’s age, height, body mass index, smoking status, epidural use, and the baby’s gestational age and head circumference. The rate of having a low Apgar score went up in a stair-step manner with the length of pushing time. The researchers didn’t find an increase in low Apgar scores with prolonged pushing phases in babies born with the use of vacuum or forceps. Table 1: Altman et al.’s (2015) findings on the length of the second stage of labor and low Apgar scores at 5 minutes In 2017, Sandström et al. conducted a follow-up study of over 42,500 Swedish birth records from 2008 to 2013. Again, they included only first-time mothers giving birth to a live singleton child at term in head-first position. They excluded elective Cesareans and Cesareans during the first stage of labor but included medical labor inductions. As before, participants were divided into five groups based on the length of the second stage: <1 hour, 1 to <2 hours, 2 to <3 hours, 3 to <4 hours, and 4 hours. This time, they looked at three types of adverse newborn outcomes: acidosis (too much acid in baby’s blood), asphyxia-related complications (such as seizures or meconium aspiration), and admission to the NICU. Compared with a second stage of labor of <1 hour, a second stage 4 hours was associated with almost a 2.5-fold increased risk of asphyxia-related complications and an 80% increased risk of admission to the NICU even after taking mother-baby characteristics and birth interventions into account. They found no association between the length of the second stage and risk of acidosis but did find that the length of time spent actively pushing was related to increased rates of acidosis. This study found that newborn risks increase with length of the second stage; however, the overall rates of bad outcomes were low.

Prolonged Pushing Phases in California, U.S.

In 2007, Cheng et al. specifically looked at the records of experienced mothers who pushed for longer than 3 hours between the years 1991 and 2001. They found that experienced mothers who pushed for 3 or more hours had higher rates of vacuum and forceps delivery, Cesarean, 3^rd and 4^th 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; however, the newborn risks were low overall for both groups. For example, babies born after 3 or more hours of pushing had a NICU admission rate of 5.4%, compared to 2.9% in babies who were born after less than 1 hour of pushing. The authors concluded that for experienced mothers, the risks of a prolonged pushing phase begin to outweigh the benefits starting at around 2 or 3 hours of pushing.

Prolonged Pushing Phases in Nova Scotia, Canada

In 2009, Allen et al. looked at the health records of 121,517 low-risk people who gave birth in Nova Scotia between 1988 and 2006. About half of the participants were first-time mothers and half were experienced. Fifteen percent of the first-time mothers pushed for more than 3 hours, and 3% of experienced mothers pushed for more than 2 hours—all of the people with longer pushing phases had epidurals. 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 3^rd or 4^th degree tears), postpartum hemorrhage, wound complications, and fever—even after taking into account other factors such as epidural and antibiotic use. 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 people 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 from the Allen et al. study seem ominous, most of the increased risks 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.

Prolonged Pushing Phases from across the U.S.

In 2014, Laughon et al published information on more than 43,000 first-time mothers and 59,000 experienced mothers in the U.S. In this study, they compared differences between laboring people who pushed for longer times and those who did not, based on the old ACOG guidelines. Pushing times that fell outside of the old guidelines were designated as prolonged second stage of labor. In the old guidelines, labor arrest for first-time mothers in the second stage was defined as pushing for > 3 hours with an epidural and > 2 hours without an epidural, and for experienced mothers it was defined as > 2 hours with an epidural and >1 hour without an epidural. The new ACOG/SMFM guidelines give people at least one additional hour in each category. Laughon et al. only included people who were pregnant with a single baby, in head-first position, at term, who reached 10 cm dilation. They did not include those with stillbirths prior to labor, congenital anomalies, or who had prior Cesarean surgery. Most of the study participants had an epidural (81% of first-time mothers and 73% of experienced mothers), and about 10% of first-time mothers and 4% of experienced mothers had a prolonged second stage based on the old ACOG guidelines. The results showed that the vast majority of people had a vaginal birth. For first-time mothers who reached 10 cm, 79.9% to 97.9% of the group with epidurals, and 87% to 99.4% of the group without epidurals, had vaginal births. In looking at experienced mothers, even more people who reached 10 cm had vaginal births—88.7% to 99.9% of the group with epidurals, and 96.2% to 99.9% of the group without epidurals. As you can see in the table below, people with pushing phases longer than the old ACOG guidelines tended to have higher rates of maternal and newborn health problems, although rates of most complications were low overall in all groups. Some of the complications may have been partly due to the fact that people with prolonged pushing phases were more likely to have Cesareans, vacuum, or forceps delivery. However, when the researchers did an additional analysis that only looked at first-time mothers with an epidural who did NOT have a Cesarean or instrumental delivery, there were still higher rates of some complications such as maternal infection, postpartum hemorrhage, 3rd or 4th degree tears, low Apgar scores, NICU admission, and newborn infection. This means that the Cesareans and vacuums/forceps were not the only explanation for higher rates of complications in people with prolonged pushing phase. To see the exact risks, see the table below with more detailed info from Laughon et al.’s study. Table 2: Laughon et al.’s (2014) findings on the length of the second stage of labor and health outcomes *One of the limitations of Laughon’s study is that it is not known whether some of the participants had delayed pushing. This means that some people were not actually pushing during part of their allotted time, while other people were. Also, in their discussion, the authors mentioned that the increased risk may not be due solely to the prolonged pushing phases, but that the underlying reason for the prolonged pushing phase may also cause problems. Finally, they concluded that, “…it was reassuring that for mothers with an epidural who comprised the large majority of our cohort, there was no increased risk of perinatal death or HIE [brain damage] in association with prolonged second stage.”

Another Study Looks at Prolonged Pushing Phases in California

In a 2014 study, Cheng et al. analyzed a medical database that included information from more than 42,000 people who gave birth at the University of California San Francisco between 1976 and 2008. The researchers included people who reached 10 cm dilation and gave birth to live, singleton babies in head-first position. People were excluded if they had a planned Cesarean or congenital anomalies. The researchers used the median (half-way point) and 95^th percentile (the length of the second stage by which 95% of women had already given birth, considered the upper range of normal) to report the length of labor, rather than the average length of labor.

Median means that half of the people have labor lengths longer than the median number, and half have labor lengths shorter than that number. This is the appropriate number to use when you have numbers that do not fit a perfect bell curve—and the length of the second stage labor does not make a bell curve—which is the case here, as some people have very short second stages and others have very long second stages. Because the purpose of this study was to look at the effects of epidurals on the length of the second stage, the researchers compared the characteristics of people with and without epidurals. About half of the participants in the study had an epidural and the other half did not. A higher percentage of people with epidurals were first-time mothers (60% vs. 40% among people without epidurals). Of those who had epidurals, 68% were induced and 76% had labor augmented. Among people without epidurals, 32.5% were induced and 24.2% had labor augmented. During the years when this study took place, it was routine practice at their hospital to instruct laboring people to immediately begin pushing when they reached 10 cm dilation. The researchers found that among first-time mothers who did not have an epidural, half gave birth within 47 minutes of the start of pushing, and the other half did not. But when they looked at first-time mothers who had an epidural, the median was 120 minutes, meaning that half gave birth within 120 minutes (2 hours), while the other half had second stages of labor longer than 2 hours. When they looked at the 95^thpercentile, which could be considered the upper realm of normal, the 95^th percentile was 197 minutes in people without epidurals and 336 minutes with an epidural. This means that there was a 2-hour-and-19-minute difference in the 95^thpercentile lengths of second stage labors between first-time mothers with and without epidurals. Not surprisingly, people who had given birth before had shorter second stages of labor than first-time mothers. However, the use of epidurals was still associated with longer second stages of labor in this group. The median length of the second stage of labor in experienced mothers was 38 minutes in people with epidurals and 14 minutes in those without epidurals. When they looked at the 95^th percentile, the length was 255 minutes in people with epidurals and 81 minutes in people without epidurals. The researchers then classified the participants’ labors as prolonged pushing vs. no prolonged pushing based on three different definitions of prolonged pushing—the 2003 ACOG guidelines, the newer ACOG/SMFM consensus statement that gives people one additional hour, and the 95^th percentile from this study. No matter which definition of prolonged pushing was used, there was no increase in risk of low 5-minute Apgar scores, low umbilical cord pH, meconium aspiration syndrome, sepsis, or NICU admission. However, they did find an increased risk of birth trauma with all 3 definitions of prolonged pushing. Birth trauma was defined as any case of hematoma on the head, laceration on the head, collarbone fracture, skull fracture, facial nerve palsy, or brachial plexus palsy. According to the three definitions, the risk of any birth trauma increased from a range of [0.49% – 0.54%] in people without prolonged pushing to [1.01% to 1.6%] in those with prolonged pushing. The researchers also looked at the relationship between prolonged pushing and maternal outcomes such as vacuum/forceps use, Cesarean, 3^rd or 4^th degree tears, postpartum hemorrhage, and infection; the risks of all of these complications increased with all three definitions of prolonged pushing. Using the new ACOG/SMFM consensus statement definition of prolonged pushing, the risk of 3^rd or 4^th degree tear increased from 7.8% without prolonged pushing to 17.2% with prolonged pushing; the risk of postpartum hemorrhage increased from 6.9% to 16.9%; and the risk of chorioamnionitis increased from 5.1% to 15.2%.

In their conclusion, the authors stated that having an epidural lengthens the 95^th percentile of pushing time by more than 2 hours. Because people with epidurals tend to have much longer pushing phases, and because the rates of newborn complications do not increase with longer pushing phases (with the exception of a broad definition of birth trauma, which increased from about 0.5% of newborns to about 1.3% of newborns), they believe that their study supports the use of the longer time period given for pushing in the new ACOG/SMFM consensus statement. However, they caution that allowing one additional hour with epidural use may not be sufficient. In 2015, Hung et al. looked at the length of the second stage in Taiwanese women who gave birth vaginally to healthy babies between the years 1991 to 1995, and 2010 to 2014. In order to be included in the study, women had to give birth vaginally to a live, singleton baby at term in head-first position. Women were excluded for congenital anomalies, labor induction, post-term pregnancy, if they gave birth by cesarean, if their baby was admitted to the NICU or had a 5-minute Apgar score <7, or if the mother was planning a vaginal birth after Cesarean (VBAC). In the end, there were 10,721 women in the study who gave birth from 1991 to 1995 (“1990s”), and 3,734 women who had given birth during 2010 to 2014 (“2010s”). In this hospital, all births were attended by physicians, and all laboring people were offered epidurals. Compared to the 1990s group, women who gave birth in the 2010s tended to be older, more likely to be having their first baby, have a higher body mass index, and have higher rates of epidural use and gestational diabetes. They also had less weight gain during pregnancy, earlier births, and lower birth weights. During the two time periods, the study’s overall Cesarean rate went up from 38.9% to 42.4%, and the primary Cesarean rate also went up from 18% to 25.2%. The researchers found that the median and 95^th percentile of the second stage of labor increased over time. In first-time mothers with an epidural, the median length of the second stage increased from 62 minutes in the 1990s group to 73 minutes in the 2010s group, while the 95^th percentile was 165 minutes in the 1990s and 255 minutes in the 2010s. First-time mothers who gave birth without epidurals had notably shorter pushing times; the median was 31 minutes in the 1990s group and 45 minutes in the 2010s group, while the 95^th percentile was 107 minutes in the 1990s group and 152 minutes in the 2010s group. When the researchers carried out an analysis to figure out why pushing times were longer, the main risk factors they found for a longer pushing phase were maternal age, birth weight, and the time period itself. The researchers proposed that perhaps there was something about obstetric practice that changed over the different time periods, between the 1990s and 2010s, that had an impact on the length of pushing times. In 2016, Grobman et al. studied medical records from more than 53,000 people who gave birth in the United States at 25 different medical centers between the years 2008 and 2011. People could be in this study if they were pregnant with a single, head-first baby at term, and if they reached 10 cm. People could not be in the study if they had a prior Cesarean. Pushing was defined as the time from when the mother started pushing until the baby was born (either vaginally or by Cesarean). They did not include delayed pushing (waiting for the baby to descend before instructing the mother to push) in this time period. Participants were put into five pushing groups: <1 hour, 1 to <2 hours, 2 to <3 hours, 3 to <4 hours, and 4 hours. About half of the participants were first-time mothers, and the other half had given birth vaginally before. Very few first-time mothers pushed for more than 3 hours (about 5%), and no one who had given birth before pushed for more than 3 hours. The majority of people in this study had epidurals (over 90%). Although the chances of having a Cesarean went up with longer pushing times, the majority of people who pushed for a long time period still had a vaginal birth. For example, of the 460 first-time mothers who pushed for 4 hours or longer, 357 (78%) still had a vaginal birth (although 151 of these were vacuum or forceps-assisted births). The rates of postpartum hemorrhage and 3^rd or 4^th degree tears also increased with longer pushing times. For example, the risk of having a postpartum hemorrhage was 3.7% in people who pushed for 3 to 4 hours compared to 1% in people who pushed for <1 hour, and the risk of a 3^rd or 4^th degree tear was 15% in people who pushed for 3 to 4 hours, compared to 5% in people who pushed for <1 hour. There were some increases in risks to the newborn, as well, including brachial plexus palsy, seizure, hypoxic brain injury; however, all of these rates were extremely low overall. In first-time mothers, the risk of brachial plexus injury was 0.1% in people who pushed for less than 1 hour, and 0.5% in those who pushed for 3 to 4 hours. The risk of seizure was 0.1% in people who pushed less than 1 hour, 0.3% in people who pushed for 3-4 hours, and 1.1% in those who pushed for 4 hours or greater. The risk of hypoxic brain injury was 0.3% in people who pushed less than 1 hour, 0.4% in people who pushed 1-2 hours, 0.6% in people who pushed 2-3 hours, 0.8% in people who pushed 3-4 hours, and 1.1% in those who pushed 4 hours or greater. There was only one newborn death among the first-time mothers and one among people who had given birth vaginally before, and both of these deaths occurred with less than one hour of pushing. The authors concluded, like others have before them, that the vaginal birth rate is high among people with prolonged pushing periods, and that although the risk of complications goes up, the overall complication rate for babies is low—about 2.5% for babies who are born to first-time mothers who pushed for 3 hours or greater. The main risk to the mothers with prolonged pushing seems to be the risk of 3^rd or 4^th degree tears, which increases from 5% in first-time mothers who push for less than 1 hour, to 14-16% in mothers who push for 2 hours or greater. The risk of postpartum hemorrhage remained low (<4%) even in mothers who pushed for 4 or more hours.

What do guidelines say about the length of the second stage of labor?

Because of all of the updated research evidence that has come out within the past 10 years, the proposed definitions for normal and abnormal length of labor were revised. In 2012 and again in 2014, ACOG, the Society for Maternal Fetal Medicine, and the National Institute for Maternal and Child Health issued new definitions of what they call “arrested labor” in the second stage (Spong et al. 2012; ACOG et al. 2014). The new guidelines state, “A specific absolute maximum length of time spent in the second stage of labor beyond which all women should undergo operative delivery has not been identified” (ACOG et al. 2014); (Spong, Berghella et al. 2012). The new guidelines also state that before labor arrest is diagnosed in the second stage of labor, “if the maternal and fetal conditions permit, allow for the following: At least 2 hours of pushing in multiparous women; At least 3 hours of pushing in nulliparous women; Longer durations may be appropriate on an individualized basis (e.g., with the use of epidural analgesia or with fetal malposition) as long as progress is being documented” (ACOG et al., 2014).