Managing the second stage of labor: An evidence-based approach
Continuously assessing and monitoring maternal, fetal, and modifiable factors in the second stage of labor may aid clinicians in weighing the appropriateness of expectant management against operative delivery
Factors to assess and monitor in the second stage
When assessing progress in the second stage of labor, consider:
- maternal factors
- fetal/neonatal factors, and
- modifiable factors.
Maternal factors that influence the second stage of labor include parity, body mass index (BMI), age, and clinical pelvimetry.11,16-19 Fetal/neonatal factors that impact the second stage include the estimated fetal weight, fetal presentation (cephalic, face, and so on), position, and station, as well as the FHR Category.20, 21 Factors that can be modified in the second stage include the effect of epidural analgesia (turning it down to reduce motor blockade while maintaining sensory pain relief so that patients feel the “urge” to push), maternal pushing position and technique, the presence of maternal support person(s), manual rotation for a fetal position that is not optimal, immediate versus delayed pushing, and prevention of perineal tears.22-32 Interestingly, epidural analgesia, parity, birth weight, and station at complete dilation predicted second stage duration but accounted for only 25% of the variability in second stage length, leaving 75% of the variance unexplained.16
A specific absolute maximum length of time spent in the second stage of labor beyond which all women should undergo operative delivery has not been identified.1 Therefore, maternal, fetal/neonatal, and modifiable factors need to be critically assessed and continually monitored to determine whether a prolonged second stage or an operative delivery is warranted to prevent or minimize adverse maternal and neonatal outcomes.
Maternal factors
Maternal age correlates directly with the length of the second stage. That is, the length of the second stage increases with increasing age.17
Multiparous women have a shorter length of the second stage, regardless of epidural analgesia, compared with nulliparous women.11 In the Consortium for Safe Labor, multiparous women had a significantly shorter median second stage compared with nulliparous women.11
In adjusted analyses, maternal obesity was associated with an increased risk for CD, with the risk of CD more than 3 times greater in women with a BMI higher than 40 kg/m2 compared with those who had a BMI less than 25 kg/m2.18 There were no significant differences in the length of the second stage of labor by BMI catgeories.19
Fetal factors
Birth weight greater than 4,000 g was associated with an increased risk for arrest of descent during the second stage.33
Persistent fetal occiput posterior or transverse position may impact the duration of the second stage. A retrospective cohort study in women who underwent a trial of manual rotation compared with expectant management during the second stage of labor with the fetus in occiput posterior or occiput transverse position found that women with manual rotation were less likely to have a CD, severe perineal laceration, postpartum hemorrhage, and chorioamnionitis. However, an increased risk of cervical laceration was associated with manual rotation.20
Regarding FHR status, FHR abnormalities occurred in 91% of second stage labor patterns, with Category II being the most common.21 The fetal status should remain reassuring to allow for continuation of the second stage.
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