Table 3. Association between duration of expulsive efforts and risk of PPH–univariable and multivariable analyses (n = 4389; 3688 PPH and 701 controls).

Variables	crude OR OR[95% CI]	Adjusted OR* OR [95% CI]	p
Duration of expulsive efforts (minutes)
≤18	1	1
]18–27]	1.35 [1.10–1.67]	1.17 [0.92–1.48]
]27–37]	1.78 [1.38–2.30]	1.32 [0.99–1.76]
>37	2.06 [1.53–2.77]	1.39 [0.99–1.96]
Missing	0.83 [0.66–1.03]	0.62 [0.47–0.83]	<0.01
Maternal age
≤25	1.04 [0.86–1.24]	1.08 [0.88–1.33]
26–35	1	1
>35	1.40 [1.04–1.90]	1.29 [0.93–1.78]	0.27
Gestational age
<37 weeks	0.78 [0.52–1.17]	1.17 [0.73–1.86]
37–40	1	1
≥41	1.50 [1.23–1.83]	1.11 [0.88–1.40]	0.56
Induction of labor	1.47 [1.21–1.80]	1.23 [0.96–1.56]	0.10
Total dose of oxytocin (IU)
0	1	1
]0–0.57]	1.16 [0.91–1.46]	1.16 [0.89–1.52]
]0.57–1.68]	1.38 [1.11–1.72]	1.26 [0.97–1.64]
>1.68	2.14 [1.73–2.66]	1.58 [1.19–2.10]	0.01
Epidural	1.38 [1.11–1.73]	0.85 [0.64–1.13]	0.27
Duration of previous phases of labor (for one hour)	1.10 [1.07–1.13]	1.04 [1.01–1.08]	0.01
Mode of delivery
Spontaneous	1	1
Forceps	2.02 [1.65–2.48]	1.58 [1.24–2.02]
Vacuum	1.09 [0.83–1.45]	0.83 [0.59–1.76]	<0.01
Episiotomy	1.65 [1.41–1.94]	1.74 [1.38–2.18]	<0.01
Perineal tears	1.09 [0.92–1.30]	1.63 [1.29–2.06]	<0.01
Prophylactic postpartum oxytocin administration	0.52 [0.44–0.62]	0.48 [0.39–0.59]	<0.01
Birth weight (grams)
≤3000	0.61 [0.51–0.74]	0.67 [0.54–0.84]
3001–3500	1	1
3501–4000	1.42 [1.17–1.73]	1.24 [0.99–1.54]
>4000	2.71 [1.73–4.25]	2.23 [1.37–3.61]	<0.01
Annual number of deliveries in the unit
≤1500	0.68 [0.52–0.88]	0.83 [0.46–1.50]
1501–3000	0.71 [0.55–0.91]	0.80 [0.44–1.46]
>3000	1	1	0.77
Group of randomization in PITHAGORE6 trial	0.80 [0.68–0.93]	0.89 [0.66–1.20]	0.45

* multilevel logistic regression model including all variables in the table