Contemporary estimates of median and 95^th percentile in hours by parity

	Parity 0 Median number of hours (95^th percentile)	Parity 1 Median number of hours (95^th percentile)
Change in cervix
From 4 to 5 cm	1.3 (6.4)	1.4 (7.3)
From 5 to 6 cm	0.8 (3.2)	0.8 (3.4)
From 6 to 7 cm	0.6 (2.2)	0.5 (1.9)
From 7 to 8 cm	0.5 (1.6)	0.4 (1.3)
From 8 to 9 cm	0.5 (1.4)	0.3 (1.0)
From 9 to 10 cm	0.5 (1.8)	0.3 (0.9)
Duration of second stage
Second stage with epidural analgesia	1.1 (3.6)	0.4 (2.0)
Second stage without epidural analgesia	0.6 (2.8)	0.2 (1.3)

Note the 95^th percentile for duration of time to dilate from 4 to 6 cm is almost 10 hours in nulliparous women.

Data from: Zhang J, Landy HJ, Branch DW, et al. Contemporary patterns of spontaneous labor with normal neonatal outcomes. Obstet Gynecol 2010; 116:1281.

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Contemporary estimates of median and 95th percentile in hours by parity

Contemporary estimates of median and 95^th percentile in hours by parity