Table 1.

Description of included studies

Study	Study type	Sample size	Mean age, years	Country	Baseline anemia, %	Exposure cutoff for hemoglobin, g/L	Outcome, definition	Lindings, Odds ratio (95% CI)	p-Value	Confounders adjusted	Study quality
Butwick et al.21	Cohort	1789	NA	United States	43	<110 ≥110 <100 ≥100 ≥110 100—<110 <100	PPH, estimated blood loss >1000 mL	0.40 (0.33, 0.48) Ref 0.92 (0.71, 1.17) Ref Ref 0.50 (0.39, 0.64) 0.25 (0.19, 0.32)	<0.0001 0.48 <0.0001 <0.0001	None	Poor
						<110 ≥110	Severe PPH, estimated blood loss >1500 mL	Ref 0.35 (0.27, 0.45)	<0.0001
						<100 ≥100		Ref 0.28 (0.19, 0.41)	<0.0001
						≥110 100—<110 <100		Ref 0.46 (0.34, 0.63) 0.23 (0.15, 0.34)	<0.0001 <0.0001
Geethoed et al.22	Cohort	309	22	Ghana	51	<80 ≥110	PPH, estimated blood loss >500 mL	0.96 (0.46, 2.01) Ref	0.93	None	Poor
Gonzales et al.23	Cohort	379, 816	NA	Peru	18	<110 ≥110 <70 70 to <90 90 to <110 110 to 145 >145	PPH, estimated blood loss >500 mL	1.21 (1.08, 1.36) Ref 6.15 (3.86, 9.78) 2.62 (2.03, 3.38) 1.01 (0.88, 1.15) Ref 0.84 (0.67, 1.05)	0.0008 0.002 0.002 >0.05 - >0.05	None Age, education, marital status, BMI, prenatal care, parity, gestational diabetes mellitus, cardiopathy in current pregnancy, gestational age at which hemoglobin was first measured, and recent migration	Poor
Kebede et al.24	Cohort	422	NA	Ethiopia	14	<110 ≥110	PPH, based on clinician diagnosis	7.4 (3.6, 15.3) Ref	<0.05	Confounders adjusted for but list not provided	Moderate
Luis et al.25	Case–control	212	27	UK	50	<80 ≥110	PPH, estimated blood loss >500 mL if vaginal delivery and >1000 mL if cesarean	2.64 (1.26, 5.55) Ref	0.01	None	Moderate
Malhotra et al.26	Cohort	447	27	India	7	<110 ≥110 ≥110 100—<110 70—<100 <70	PPH, definition not specified	1.53 (0.17, 13.8) Ref Ref 0.29 (0.01, 8.56) 4.82 (0.49, 47.1) 4.07 (0.25, 66.9)	0.70 0.47 0.18 0.33	None	Poor
Nyflot et al.27	Case–control	3123	33	Norway	4	<90 ≥90	Severe PPH, estimated blood loss >1500 mL or requiring blood transfusion	4.27 (2.79, 6.54) Ref	<0.001	Previous PPH, anticoagulant medication, severe preeclampsia, uterine fibromas, multiple pregnancy, mode of delivery, IVF, fever, induction of labor, birthweight >4500 g, parity	Moderate
Parks et al28	Cohort	92 247	NA	India and Pakistan	88	<110 ≥110 ≥110 100—<110 70—<100 <70	PPH, based on clinician diagnosis	0.78 (0.63, 0.96) Ref Ref 0.65 (0.52, 0.82) 0.82 (0.66, 1.02) 5.31 (3.51, 8.02)	0.018 0.0003 0.07 <0.0001	None	Moderate
Rukuni et al.29	Cohort	80 422	29	Scotland	9	<100 ≥100	PPH, estimated blood loss >500 mL	0.92 (0.86, 0.98) Ref	0.007	Age, parity, smoking status, ethnicity, socioeconomic status, BMI and CKD	Moderate
Selo-Ojeme et al.30	Case–control	208	NA	Nigeria	5	<110 ≥110	PPH, estimated blood loss >500 mL	1.29 (0.38, 4.36) Ref	0.68	None	Poor
Soltan et al.31	Cohort	152	25	Egypt	76	<110 ≥110 ≥110 100—<110 70—<100 <70	PPH, estimated blood loss >500 mL	7.78 (0.45, 134) Ref Ref 0.38 (0.01, 19.2) 80 (4.36, 1468) 384 (5.95, 24 784)	0.16 0.63 0.003 0.005	None None	Poor
Tort et al32	Cohort	3278	NA	Senegal and Mali	NA	<70 ≥70	Mortality among women with PPH; PPH defined based on clinician diagnosis	6.65 (3.77, 11.7) Ref	NA	Country, location in relation to hospital, age, number of prenatal visits, preexisting disease, gestational hypertensive disorders, referral, prolonged labor, mode of delivery and birthweight	Moderate
Wandabwa et al.33	Case–control	606	24	Uganda	8	<110 ≥110	PPH, estimated blood loss >500 mL, or any vaginal bleeding with hemodynamic deterioration	6.10 (1.10, 35.4) Ref	0.05	Age, distance from home to hospital, marital status, educational level, job, spouse job, type of house, need to request permission to visit hospital, who pays for treatment, previous CS, PPH, number of pregnancies	Poor

Abbreviations: BMI, body mass index; CKD, chronic kidney disease; IVF, in vitro fertilization; NA, not available.