Reported in an article by KJ Dell’Antonia in the New York Times on April 2, 2012, “births during the last decade take longer than they did in the early 1960s;” 2.6 hours longer for women having their first baby, and a little less than two hours longer for women who have given birth before.”

“Scientists at the National Institute of Child Health and Human Development compared the birth experiences of thousands of women who went into labor without complications from 1959 to 1966 with those of women from 2002 to 2008, and found that women in the latter group labored longer, and were more likely to have had medical interventions, like an epidural or a dose of oxytocin.”  The researchers are unsure if interventions such as epidural anesthesia are responsible for the longer labors, or are other variables that were not examined in the study at play?  Are longer labors necessarily a bad thing? To read more, go to the story in “Motherlode” in the Times: http://parenting.blogs.nytimes.com/2012/04/02/why-are-women-spending-more-time-in-labor/?scp=1&sq=why%20is%20labor%20longer&st=cse or to the original article in the American Journal of Obstetrics and Gynecology entitled “Changes in Labor Patterns Over 50 Years, online at http://www.sciencedirect.com/science/article/pii/S0002937812002736?v=s5.

001fSo how long is “normal” labor?  For years, obstetric textbooks have used the labor curve established in the 1950s by a Emanuel Friedman, an obstetrician who analysed 500 young, first-time moms during their labors in 1954, and produced a graphical representation of an ‘ideal’ labor, which remains known as the “Friedman curve”.   Every obstetrician, nurse-midwife, and labor nurse who works in a hospital is familiar with this curve and with women whose labors have “fallen off the curve.”   For fifty years, this curve was seen as the yardstick by which to measure the normalcy of all labors.  It was the impetus for decision to start a synthetic oxytocin drip to augment a protracted labor, and to “move to cesarean” when augmentation did not produce a delivery in the allotted amount of time.  In other words, Friedman’s curve has been at least partly responsible for the “cascade of interventions” so familiar to the hospital-based midwife, and for the related terminology related implying a pathological condition that requires a medical intervention – “protraction and arrest disorders,” “fallen off the curve,” “failure to progress,”  etc.

Friedman’s curve, however, was not based on rigorous data – it included only a small group of similar women, and used subjective measurements of cervical dilatation.  There were never replications of the original research with other groups of women to validate the findings.  Friedman himself said that his study was not intended to provide an absolute criterion for labor progress.  Over the years, there were other developments that certainly affected the validity of the Friedman curve.  During the period when he gathered his data, episiotomy was almost universal, forceps deliveries were common.  Both of these interventions artificially shortened the length of labor.  More recently, epidural anesthesia has become much more common and is known to increase the length of labor, and average weights of both mothers and babies have increased.

By the onset of the 21st century, birth attendants, obstetricians and midwives alike, were starting to question whether Friedman’s curve was “the golden rule”  and could be applied to all laboring women. In 2000, Elaine Diegmann and her midwifery colleagues studied Puerto Rican and African American women in New Jersey and found that they had shorter second stages of labor than white women – the women used in Friedman’s study.   In 2002,  the curve was  challenged in a study by J Zhang and colleagues,  ‘Reassessing the labor curve in nulliparous women.   In the 2012 study referenced in the New York Times article above, the authors came up with a very different curve, not only allowing more time for various phases and stages of labor, but showing different rates of acceleration and deceleration of labot intensity. In a separate article on contemporary cesarean deliveries, Dr Zhang concluded that, to “decrease cesarean delivery rates in the United States, reducing primary cesarean delivery is the key.  Increasing vaginal birth after previous cesarean rate is urgently needed.  Cesarean section for dystocia should be avoided before the active phase is established, particularly in nulliparous women and in induced labor.”

Common sense admits that there must be a point at which a labor is called “prolonged,” and an intervention must be initiated.  The problem is in identifying if and when this occurs in individual women.  So many factors play into this decision.  Perhaps the “intuition” of the practitioner, midwife or physician, really should count for more, and any graph or rule should count for less.

For a more comprehensive discussion of Friedman’s curve, failure to progress, and unplanned cesareans, go to the online article from August 28, 2013 by Rebecca Dekker, Phd, RN, APRN at www.EvidenceBasedBirth.com.

For a related post on this website in 2008 on a presentation at the ACNM Annual meeting that year on the length of normal labor by Leah Albers, CNM, DPH, go to How Long Is Normal Labor?

References

Diegmann EK, Andrews CM, Miemczura CA (2000).  The length of the second stage of labor in uncomplicated, nulliparoous African American and Puerto Rican women. Journal of Midwifery and Women’s Health 45(1):67-71.

Friedman, EA (1955). “Primigravid labor; a graphicostatistical analysis.” Obstet Gynecol 6(6): 567-589.

Friedman EA (1978).  Labor: Clinical evaluation and management (New York: Appleton-Century-Crofts)

Laughon SK, Ware Branch D, Beaver J, Zhang J. (2012) Changes in Labor Patterns Over Fifty Years. American Journal of Obstetrics & Gynecology 206:5(419.e1-419.e9.

Zhang J et al. ‘Reassessing the labor curve in nulliparous women’, American Journal of Obstetrics and Gynecology, 187 (October 2002), pp 824-828

Zhang J, Troendle J, Reddy UM, et al, for the Consortium on Safe Labor. Contemporary cesarean delivery practice in the United States. Am J Obstet Gynecol 2010;203:326.e1-10.