Table 2. Univariate and multivariate analysis of risk factors to blood loss ≥ 500mL and ≥ 1000mL in 2 hours.

		500 mL within 2 hours		1,000 mL within 2 hours
	n	OR	p-value	OR	p-value
		(95%CI)		(95%CI)
Univariate analysis
Age
≤ 19 years old	63	1.51	0.172	1.60	0.329
		(0.83 - 2.71)		(0.62 - 4.11)
20–35 years old	191	Ref.
≥ 35 years old	16	1.00	0.990	1.67	0.516
		(0.34 - 2.99)		(0.35 - 7.87)
Ethnicity
white	178	Ref.
non-white	85	0.83	0.534	2.24	0.085
		(0.47 - 1.47)		(0.89 - 5.61)
Schooling (mean in years)	231	1.04	0.431	0.97	0.813
		(0.93 - 1.17)		(0.80 - 1.18)
Overweight (BMI a ≥25)	104	1.36	0.272	0.94	0.900
		(0.78 - 2.36)		(0.34 - 2.55)
Obesity (BMI a  ≥ 30)	89	1.03	0.913	1.60	0.350
		(0.58 - 1.82)		(0.59 - 4.31)
Multiparity (two or more previous deliveries)	53	0.65	0.227	0.87	0.817
		(0.32 - 1.30)		(0.28 - 2.70)
Gestational age
34–40 weeks	146	0.92	0.764	1.64	0.277
		(0.53 - 1.59)		(0.67 - 4.03)
40 weeks	102	Ref.
Previous C-section	42	1.13	0.731	1.65	0.351
		(0.56 - 2.28)		(0.57 - 4.75)
Anemia (hemoglobin ≤ 11 g/dl)	43	1.60	0.175	2.82	0.037
		(0.81 - 3.15)		(1.06 - 7.47)
Spontaneous labor	203	0.58	0.062	0.87	0.780
		(0.32 - 1.03)		(0.32 - 2.32)
Duration of second-stage of labor ≥ 30 minutes	223	1.88	0.032	1.90	0.230
		(1.05–3.37)		(0.66–5.45)
Anesthesia (yes)	168	1.225	0.458	1.068	0.886
		(0.71–2.09)		(0.43–2.64)
Episiotomy (yes)	96	2.39	0.001	3.05	0.017
		(1.39 - 4.10)		(1.12 - 7.66)
Laceration (≥ grade 2)	144	1.03	0.924	1.64	0.300
		(0.60 - 1.74)		(0.64 - 4.22)
Forceps (yes)	23	9.87	<0.001	2.68	0.101
		(3.53 - 27.65)		(0.82 - 8.72)
Multivariate analysis
Forceps (yes)	260	9.48	<0.001
		(2.85 - 31.53)
Duration of second stage of labor ≥ 30 minutes	260	1.05	0.883
		(0.57–2.10)
Episiotomy (yes)	260	1.49	0.25
		(0.75–2.96)

Abbreviations: BMI, body mass index; CI, confidence interval; OR, odds ratio.