My first labor was long. Really long. It lasted from Friday night to Sunday evening. Pain I had anticipated, prepared for, given myself multiple pep talks for, but the duration… It undid me.
As I recently watched a good friend go through a similar labor, some old nagging questions resurfaced: How uncommon is it for women to labor for days? What is a “normal” length of labor, if such a thing exists?
Oddly enough, the medical answers to these questions have just changed dramatically. This is because of a recently completed landmark study of nearly 100,000 labors. The study, which used medical record data collected between 2002 and 2008 from hospitalsm across the U.S., showed unequivocally that we labor much more slowly than we used to. Much, much more slowly.
In fact, our labors have slowed down so much that in 2014 the American College of Obstetricians and Gynecologists (ACOG) revised its definitions of normal and overly slow labor. Until then, the definitions were based on data from the 1950s and 1960s. These data were used to define a “normal” labor duration, how long it takes most women in active labor to reach a full 10 cm of dilation and then to push the baby out. By the same token, these data were used to defined abnormal labor: labors that lasted longer than 19 out of 20 of these labors (the 95th percentile for duration) were considered overly slow or stalled.
The easiest way to see how much our labors have slowed down is look at how long it takes for women in labor to completely dilate. Below are the averages in 1959-1966 and in 2002-2008.
Note that these are the averages among women who delivered a single baby (no twins or higher order multiples) and who delivered vaginally (not by c-sections). First births tend to take longer, so separate plots are given for first-time, second-time, and third-or-more-time mothers.
For first-time mothers:
For second-time mothers:
For third-or-more-time mothers:
Compared to our own labors, our grandmothers’ are downright zippy, reaching full dilation an average of about 2 hours earlier.
The average curves in 2002-2008 are not just slower, they also show a later acceleration. Our grandmothers’ cervical dilation accelerated around 4 cm. Cervical dilation typically begins slowly and then picks up as labor progresses. This was true back then and remains still true today. But the point at which our labors tend to speed up is now around 6 cm. This change is so pronounced and consistent that it led ACOG to revise its definition of when active labor starts. Active labor is now defined as starting when a woman reaches 6 cm instead of 4 cm.
This revision is a big deal. It flies in the face of what most of us have been taught in our birth classes and contradicts much of the information available online. It also changes when the medical clock for active labor starts. Until 6 cm, assuming your water has not broken, there is no expected duration, nor any duration that is considered too long.
So how long does the newly defined active labor phase typically last? In the 2002-2008 cohort:
Given these dramatic changes, it is no surprise ACOG felt compelled to update its guidelines. ACOG’s new and old definitions are shown below. An abnormally long labor was again defined as above the 95th percentile for duration.
The Length of Early Labor
According to ACOG’s new guidelines, if you are experiencing regular contractions but are not yet 6 cm dilated, you are in still in what is known as “latent” or early labor.
This early labor period was what made my first labor so long. I took nearly 36 hours to reach just 3 cm. I still remember how completely demoralized I felt when the nurse told me, on Sunday morning, having been in labor since Friday night.
But was my experience truly atypical? How long does this early phase of labor typically last?
Unfortunately, unlike active labor, what we know about early labor is still mired in the past.
The early phase has traditionally been considered prolonged if it lasts more than 20 hours for first-time mothers, and more than 14 hours for women who have given birth before. These estimates are probably underestimates. They derive from the 1950s and 1960s data and rely upon the old definition of 4 cm for the end of early labor/onset of active labor.
The 2002-2008 study, which was not designed to study early labor, does not provide much help here. The study relied solely on hospital records, so everything that happened prior to admission to the hospital, the time when most of early labor takes place, is a blank.
Let’s make the somewhat crude assumption that labors that start out fast continue to be fast, and those that start slow continue to be slow. Then the median time to go from 3 to 10 cm would be about 6 hours, and the 95th percentile would be about 25 hours.
This table also makes it clear to me that while my early labor the first time probably was unusually long, the rest of my labor, which lasted about 8 hours, was not.
So congratulations, you’re now fully dilated! All that remains is to push the baby out. Easy peasy, right?
ACOG currently recommends allowing at least 3 hours of pushing for first-time mothers and 2 hours of pushing in women who have previously given birth.
The median time for pushing is considerably less than this though.
The medians are very low compared to ACOG’s limits, because because the distribution of pushing times is highly skewed to the right: Most women push their babies out fairly quickly, in an hour or less, but a significant fraction of women take much, much longer.
Why do our labors take longer than our grandmothers’?
There is no one single all-encompassing explanation. But there are several known contributing factors:
- We are heavier. The average BMI at delivery in the 1950s and 1960s was around 26. Nowadays the average BMI at delivery is 29-30.
- We get epidurals. Epidurals slow down labor, especially the pushing phase. Despite this, research does not generally find that epidurals increase the rate of c-sections. So if you need pain relief, fear of a c-section is not a reason to refuse an epidural.
- We give birth later. The average age of women delivering in the 1950s and 1960s was 24; in the 2002-2008, it was 27.
- Our babies are larger. Babies in 2002-2008 weighed an average of 100 grams (~1/5 of a pound) more than those born in 1950s and 1960s.
- More frequent use of pitocin. We are much more likely to have our labors sped up with pitocin than our grandmothers: 31% of women in 2002-2008 cohort received pitocin, versus 12% in 1959-1966. Wait, wouldn’t this make our labors shorter? Yes. Pitocin is so common that it almost surely shortens the average length of labors. So our labors may have slowed down even more than the raw data suggest.
The above reasons do not fully explain why our labors are so much slower. Even when limiting comparisons of 1959-1966 and 2002-2008 deliveries to low-risk women of similar ages, BMIs, ethnicity, and labor characteristics, researchers found that:
“labor in the CSL [2002-2008] cohort was still longer. It would seem therefore that other changes in obstetric practices were likely influential.” Laughon et al. 2012
What does “other changes in obstetric practices” really mean? Essentially, this is a more sophisticated way of saying, “We don’t have a clue.”
The Bottom Line
In general, we labor much more slowly than we used to. While weight, age, and increase epidurals explain some of this slowdown, the reasons are not completely understood.
In addition, the average labor times are not the best guide for determining how long your own labor is likely to last. There is a huge range of times for each stage of labor. This, incidentally, is why I think birth plans should look more like flow charts. Women should be given a template that asks questions like: How would you like to handle a labor that lasts for 8 hours? And how would you like to handle one that lasts for over 30?
Finally, figuring out how long a labor normally lasts is not an idle personal question. In the U.S., a labor that lasts too long or stalls is the most frequent cause of c-sections among first-time mothers. It is the reason cited for 35% of first-time c-sections.
If you are hoping to avoid a c-section, it makes sense to read ACOG’s new recommendations in full. The new guidelines are significantly more lenient than the old ones and allow much more time for labor to progress on its own.
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