A reduction in the intercontraction interval is associated with active labor (strength of recommendation [SOR]: B, cohort study). Most primigravidas who have had regular contractions for 2 hours and multigravidas who have had regular contractions for 1 hour haven't transitioned into the active phase of labor (SOR: B, cohort study)

Kaufmann, Leonora

McPherson, Vanessa

Mull, Courtney

Zolotor, Adam J.

University of Missouri: MOspace

Evidence-based answers from the  Family Physicians Inquiries NetworkjFPoNlINE.com Vol 58, No 12  |  DEcEmbEr 2009  |  ThE jourNal oF FamIly PracTIcEfollowed from presentation to delivery.1 Cervical dilation was assessed by examina-tion every 30 to 120 minutes, almost always performed by the same examiner through-out labor. In primigravidas, latent labor averaged 6.4 hours, with 95% of women completing the latent phase in 20.6 hours. In multigravi-das, 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 laborA 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.3Earlier admission leads to more  interventions and poorer outcomesMany 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 retrospec-tive 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, epidu-ral analgesia, intrauterine pressure catheters, and fetal scalp electrodes, and increased rates of chorioamnionitis, postpartum infection, and  Do intercontraction intervals  predict when a woman at term should seek evaluation of labor? EvidEncE-basEd answErA no; however, a reduction in the intercontraction   interval is associated with active labor (strength of recommendation [SOR]: B, cohort study). Most primigravidas who have had regular contractions for 2 hours and multigravidas who have had regular contrac-tions for 1 hour haven’t transitioned into the active phase of labor (SOR: B, cohort study). Evidence summaryMultiple 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 ac-tive phases. The latent phase is defined as the period between onset of labor and cervical dila-tation 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 pre-dictable 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 be-ginning of fetal descent.2Latent labor was initially described in a large prospective cohort of 10,293 term gravidas (including 4175 nulliparas and 5599 multiparas) Courtney Mull, MD, and  Vanessa McPherson, MD Department of Family Medicine, University of North Carolina and Carolinas Medical Center, CharlotteAdam J. Zolotor, MD, MPHDepartment of Family Medicine, University of North Carolina, CharlotteLeonora Kaufmann, MLISDepartment of Family Medicine, University of North Carolina and Carolinas Medical Center, CharlotteONliNeExCLuSIVE676aThE jourNal oF FamIly PracTIcE  |   DEcEmbEr 2009  |   Vol 58, No 12 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, Swit-zerland: 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 pro-spective study. Med Gen Med. 2005;7:61.  4.  Holmes P, Oppenheimer LW, Wen SW. The relationship be-tween 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 assess-ment program: a randomized, controlled trial. Birth. 1998;25:5-10. referencesneonatal intubation.4,5 See the TABLE for a sum-mary of the effects of latent-phase admission. Labor assessment program reduced  time in the labor wardLabor assessment programs attempt to delay ad-mission during early active labor. One random-ized 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 sup-port 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 de-creased use of analgesics and oxytocin and re-duced time spent in the labor ward.6 RecommendationsThe American College of Obstetricians and Gynecologists (ACOG) acknowledges in pa-tient 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 hos-pital if she thinks she’s in labor.7 Similarly, a patient handout from the American College of Nurse-Midwives recom-mends calling the health care provider if con-tractions 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 oc-curring every 2 to 5 minutes, and as often as every 2 to 3 minutes.9 TABLEConsequences of hospital admission during latent vs active labor Nulliparous Parousconsequence Latent (%) Active (%) NNH Latent (%) Active (%) NNHOxytocin4 43 27 6* 20 9 9*Epidural4 82 61 5* 58 40 6*Assisted vaginal delivery427 25 50 8 6 50Cesarean4 10 4 17* 8 6 50Cesarean5† 14 7 14* 3 1 50*pH <7.14 4 3 100 3 2 100Apgar <74 4 2 50 3 2 100NNh, number needed to harm.*Indicates relationship significant at the level <.05. † Study by bailit5 also showed significant associations for oxytocin, scalp ph, intrauterine pressure catheter, fetal scalp electrode, epidural, neonatal intubation, amnionitis, and postpartum infection. raw data are unavailable for abstraction.Women  admitted during the latent phase of labor had higher rates of cesareans and increased use  of oxytocin,  epidural  analgesia,  and other  interventions.  676bcoNTINuEDjFPoNlINE.com Vol 58, No 12  |  DEcEmbEr 2009  |  ThE jourNal oF FamIly PracTIcE 676c 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. Ac-cessed 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. INTErcoNTracTIoN INTErValS

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

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