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Figure 1.Study selection process.

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Figure 2.Pooled data for randomized controlled trials in which data were recorded for the duration of first stage of labor (h).

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Figure 3.Pooled data for randomized controlled trials in which data were recorded for the occurrence of Cesarean section.

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Figure 4.Pooled data for randomized controlled trials in which data were recorded for the use of analgesia.

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Figure 5.Pooled data for randomized controlled trials in which data were recorded for labor augmentation.

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Figure 6.Pooled data for randomized controlled trials in which data were recorded for the Apgar score at the 5th minute of life.

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