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134: Natural history of labor progression

      Objective

      To describe labor patterns in a large cohort in which clinical management was more conservative and perinatal outcomes were normal.

      Study Design

      The National Collaborative Perinatal Project followed up over 55,000 pregnancies in 12 academic hospitals in the U.S. from 1959 to 1965. Detailed labor/delivery information was collected. We restricted to 28,256 deliveries that were singleton, term, spontaneous onset of labor, vertex presentation at admission, no previous cesarean section, delivered vaginally without using mid or high forceps, and 5' Apgar score >= 7. We examined duration of labor separated by parity.

      Results

      The following table presents the characteristics of the cohort and duration of labor. In nulliparas, the median duration from 4 to 10 cm was 4.9 hrs with the 95th% at 21.9 hours.
      Tabled 1
      Parity 0 (N=8,468)Parity 1 (N=6,607)Parity 2+ (N=13,181)
      Maternal age202227
      Birthweight3,1563,2293,278
      Regional analgesia62%37%20%
      Oxytocin for augment15%10%10%
      Cervical dilationDuration of labor(hour)(median, 95th%)
      4 - 51.0 (4.3)1.0 (3.9)1.0 (4.3)
      5 - 60.7 (2.6)0.6 (1.7)0.6 (2.0)
      6 - 70.5 (1.6)0.4 (1.2)0.4 (1.2)
      7 - 80.4 (1.2)0.3 (0.7)0.3 (0.7)
      8 - 90.4 (1.0)0.3 (0.7)0.3 (0.7)
      9 - 100.4 (1.2)0.2 (0.5)0.2 (0.5)
      2nd stage0.7 (2.4)0.3 (0.8)0.2 (0.6)

      Conclusion

      In vaginal deliveries with normal perinatal outcomes, duration of labor can vary widely, especially before 6 cm. Duration of active phase in nulliparas could last 22 hrs (95th%) and have normal perinatal outcomes.