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Poster session II Clinical obstetrics, diabetes, labor, medical-surgical-disease, physiology/endocrinology, prematurity: Abstracts 237 - 386| Volume 208, ISSUE 1, SUPPLEMENT , S112, January 01, 2013

242: Fetal descent: what is normal station for a given cervical exam?

      Objective

      Modern data has improved our understanding of cervical dilation progress through the first stage of labor; modern data on fetal descent during the first stage is still needed. We aimed to estimate the expected station for a given cervical dilation during the first stage by parity.

      Study Design

      We performed a retrospective cohort study of all consecutive women admitted for delivery at term (≥ 37wks) who progressed to 10cm. Known anomalies were excluded. Detailed history, labor, and delivery information was collected, including all cervical exams to allow for complete reconstruction of first stage labor curves. Because it cannot be known when a fetus progresses from one dilation and station to the next, and only the exam time at which the progress is discovered is known, interval-censoring analysis was used to estimate the median station, and 5th and 95th percentile, at a given dilation by parity. Analysis was repeated, stratified by induction (compared to spontaneous labor).

      Results

      Of 5,388 women, 1,992 were nulliparas (nullips) and 3,396 were multiparas (multips). Of these, 566 nullips and 1449 multips labored spontaneously. Overall, nullips tended to have a lower station than multips until late in the first stage. By 6cm, median station was 0 (−2, 1) for nullips and −1 (−3,1) for multips; by 8cm, 95% of nullips were at −1 station or lower. Considering only women who labor spontaneously, both nullips and multips had a median station of 0 during active labor (> 6cm) and 95% of all women were 0 station or lower at complete (Table).
      Tabled 1
      Table thumbnail grr6

      Conclusion

      Among women in first stage labor at term, there is wide variation in the expected station by increments of dilation. However, 95% of nullips entering active labor (6cm) had a fetal station of −2 or lower; above that should be considered abnormal.