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 ONLINE EXCLUSIVE: CLINICAL INQUIRIES

Evidence-Based Answers from the Family Physicians Inquiries Network

Do intercontraction intervals predict when a woman at term should seek evaluation of labor?

Department of Family Medicine, University of North Carolina and Carolinas Medical Center, Charlotte

Department of Family Medicine, University of North Carolina, Charlotte

Department of Family Medicine, University of North Carolina and Carolinas Medical Center, Charlotte

  Evidence summary

Multiple cohort studies demonstrate that the expected events of normal labor form a bell-shaped curve. The range of labor experiences makes predicting when a particular woman will enter active labor difficult.

When does latent labor become active labor?

The first stage of labor includes latent and active phases. The latent phase is defined as the period between onset of labor and cervical dilatation of 3 to 4 cm or the time between onset of regular contractions and escalation in the rate of cervical dilation. Regular contractions must be intense, last 60 seconds, and occur in a predictable pattern. Escalating cervical dilation is marked by a change in the cervical examination over a short period of time (usually 2 hours).¹

The World Health Organization defines active labor as cervical dilation between 4 and 9 cm, with dilation usually occurring at 1 cm per hour or faster and accompanied by the beginning of fetal descent.²

Latent labor was initially described in a large prospective cohort of 10,293 term gravidas (including 4175 nulliparas and 5599 multiparas) followed from presentation to delivery.¹ Cervical dilation was assessed by examination every 30 to 120 minutes, almost always performed by the same examiner throughout labor. In primigravidas, latent labor averaged 6.4 hours, with 95% of women completing the latent phase in 20.6 hours. In multigravidas, the mean duration of latent labor was 4.8 hours, with 95% of women transitioning to active labor in 13.6 hours.

Shorter intercontraction interval linked to active labor

A recently published cohort study of women presenting to labor and delivery found that a relative decrease in the intercontraction interval was associated with a diagnosis of labor (odds ratio=1.42; 95% confidence interval, 1.06-1.90). The study failed to define either active labor or decrease in the intercontraction interval.³

Earlier admission leads to more interventions and poorer outcomes

Many studies have suggested that admitting women to the hospital during the latent phase of labor is associated with more interventions and poorer outcomes. Two large retrospective cohort studies (N=2697 and 3220) found increased rates of cesarean section in women admitted during the latent phase.^4,5 They also reported increased use of oxytocin, epidural analgesia, intrauterine pressure catheters, and fetal scalp electrodes, and increased rates of chorioamnionitis, postpartum infection, and neonatal intubation.^4,5 See the TABLE for a summary of the effects of latent-phase admission.

Consequences of hospital admission during latent vs active labor

Labor assessment program reduced time in the labor ward

Labor assessment programs attempt to delay admission during early active labor. One randomized clinical trial (N=209) among low-risk women with reassuring maternal and fetal assessments in early labor divided the women into 2 groups when they presented for labor and delivery. One group received advice, encouragement, and support along with instructions to walk or return home and come back when labor became more active (defined as regular, painful contractions and dilation of at least 3 cm). The other group was admitted directly to the labor and delivery ward. The study found that early labor assessment decreased use of analgesics and oxytocin and reduced time spent in the labor ward.⁶

  Recommendations

The American College of Obstetricians and Gynecologists (ACOG) acknowledges in patient education literature that distinguishing true from false labor is difficult. ACOG lists characteristics of each and recommend that a woman monitor the frequency of contractions for an hour and call the doctor’s office or hospital if she thinks she’s in labor.⁷

Similarly, a patient handout from the American College of Nurse-Midwives recommends calling the health care provider if contractions are ≤5 minutes apart for more than 1 hour, several contractions are so painful that the woman cannot walk or talk, or her water breaks.⁸

A standard textbook describes normal uterine contractions during active labor as occurring every 2 to 5 minutes, and as often as every 2 to 3 minutes.⁹

References

1. Friedman EA, Kroll BH. Computer analysis of labor progression. 3. Pattern variations by parity. J Reprod Med. 1971;6:179–183.
2. World Health Organization. Managing Complications in Pregnancy and Childbirth: A Guide for Midwives and Doctors. Geneva, Switzerland: Department of Reproductive Health and Research, Family and Community Health, World Health Organization; 2003.
3. Ragusa A, Monsur M, Zanini A, et al. Diagnosis of labor: a prospective study. Med Gen Med. 2005;7:61.
4. Holmes P, Oppenheimer LW, Wen SW. The relationship between cervical dilatation at initial presentation in labour and subsequent intervention. BJOG. 2001;108:1120–1124.
5. Bailit JL, Dierker LR, Blanchard MH, et al. Outcomes of women presenting in active versus latent phase of spontaneous labor. Obstet Gynecol. 2005;105:77–79.
6. McNiven PS, Williams JI, Hodnett E, et al. An early labor assessment program: a randomized, controlled trial. Birth. 1998;25:5–10.
7. How to Tell When Labor Begins.  Washington, DC: American College of Obstetricians and Gynecologists; 1999. Available at: www.acog.org/publications/patient_education/bp004.cfm. Accessed November 8, 2008.
8.  Am I in Labor? Silver Spring, Md: American College of Nurse-Midwives; 2003. Available at: www.midwife.org/siteFiles/news/sharewithwomen48_4.pdf. Accessed November 7, 2008.
9. Kilpatrick S, Garrison E.   Normal labor and delivery. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia: Churchill Livingstone/Elsevier; 2007:303–317.

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