The Association Between Severity of Anemia During Pregnancy and Severe Maternal Outcomes: A Retrospective Cohort Study

Figures & data

Table 1 Baseline Characteristics and Maternal Complications by Severity of Anemia During Pregnancy

Covariates	No Anemia (n=99,755)	Mild Anemia (n=18,502)	Moderate Anemia (n=19,697)	Severe Anemia (n=602)	Total (n=138,556)
Sociodemographic characteristics
Maternal age, years	29.2 (4.7)	29.7 (4.8)	29.5 (4.9)	29.2 (5.4)	29.3 (4.8)
Marital status
Married or cohabitating	99,011 (99.3%)	18,431 (99.6%)	19,592 (99.5%)	592 (98.3%)	137,626 (99.3%)
Single, divorced, widowed, or other	744 (0.7%)	71 (0.4%)	105 (0.5%)	10 (1.7%)	930 (0.7%)
Maternal education
Primary school or below	538 (0.5%)	89 (0.5%)	110 (0.6%)	9 (1.5%)	746 (0.5%)
Middle school	18,594 (18.6%)	1443 (7.8%)	2978 (15.1%)	131 (21.8%)	23,146 (16.7%)
High school	45,182 (45.3%)	9403 (50.8%)	10,296 (52.3%)	341 (56.6%)	65,222 (47.1%)
College or above	35,441 (35.5%)	7567 (40.9%)	6313 (32.1%)	121 (20.1%)	49,442 (35.7%)
Level of hospital
Provincial	20,636 (20.7%)	6454 (34.9%)	5321 (27.0%)	65 (10.8%)	32,476 (23.4%)
Municipal	25,124 (25.2%)	5696 (30.8%)	4640 (23.6%)	122 (20.3%)	35,582 (25.7%)
County	53,995 (54.1%)	6352 (34.3%)	9736 (49.4%)	415 (68.9%)	70,498 (50.9%)
Obstetric characteristics
Pregnancies (including current pregnancy)	2.4 (1.4)	2.5 (1.4)	2.6 (1.4)	2.7 (1.6)	2.5 (1.4)
Previous births (excluding current delivery)	0.6 (0.6)	0.7 (0.6)	0.7 (0.6)	0.8 (0.7)	0.6 (0.6)
Antenatal examinations	7.9 (2.4)	8.3 (2.4)	8.0 (2.4)	7.4 (2.5)	8.0 (2.4)
Previous cesarean sections	0.2 (0.4)	0.3 (0.5)	0.3 (0.5)	0.3 (0.5)	0.2 (0.5)
Multiple pregnancies	1663 (1.7%)	471 (2.5%)	704 (3.6%)	28 (4.7%)	2866 (2.1%)
Referred in from other hospital	33 (0.0%)	12 (0.1%)	18 (0.1%)	5 (0.8%)	68 (0.0%)
Maternal complications
Hemorrhagic disorders	1552 (1.6%)	702 (3.8%)	2170 (11.0%)	220 (36.5%)	4644 (3.4%)
Infections	1929 (1.9%)	685 (3.7%)	766 (3.9%)	28 (4.7%)	3408 (2.5%)
Hypertensive disorders	4297 (4.3%)	968 (5.2%)	1209 (6.1%)	56 (9.3%)	6530 (4.7%)
Gestational diabetes mellitus	11,038 (11.1%)	2252 (12.2%)	2060 (10.5%)	49 (8.1%)	15,399 (11.1%)
Other comorbidities	2099 (2.1%)	614 (3.3%)	742 (3.8%)	29 (4.8%)	3484 (2.5%)

Figure 1 Selection of study participants.

Abbreviation: SMO, severe maternal outcomes.

Table 2 Severe Maternal Outcomes and Organ Dysfunction by Severity of Anemia During Pregnancy

	No Anemia (n=99,755)	Mild Anemia (n=18,502)	Moderate Anemia (n=19,697)	Severe Anemia (n=602)	Total (n=138,556)
Severe maternal outcomes	85 (0.1%)	30 (0.2%)	234 (1.2%)	68 (11.3%)	417 (0.3%)
Cardiovascular dysfunction	13 (0.0%)	1 (0.0%)	30 (0.2%)	19 (3.2%)	63 (0.0%)
Respiratory dysfunction	14 (0.0%)	1 (0.0%)	11 (0.0%)	3 (0.5%)	29 (0.0%)
Coagulation or hematologic dysfunction	45 (0.0%)	27 (0.1%)	206 (1.0%)	66 (11.0%)	344 (0.2%)
Renal dysfunction	4 (0.0%)	0 (0.0%)	2 (0.0%)	2 (0.3%)	8 (0.0%)
Neurological dysfunction	25 (0.0%)	2 (0.0%)	7 (0.0%)	1 (0.2%)	35 (0.0%)
Hepatic dysfunction	5 (0.0%)	0 (0.0%)	1 (0.0%)	1 (0.2%)	7 (0.0%)
Uterine dysfunction	6 (0.0%)	5 (0.0%)	12 (0.1%)	7 (1.2%)	30 (0.0%)

Figure 2 Relative contribution of maternal complications among women with different outcomes.

Note: Others refer to other comorbidities.

Abbreviations: Non-SMO, women without severe maternal outcomes; SMO, women with severe maternal outcomes; Non-MT SMO, women with non-massive transfusion severe maternal outcomes.

Table 3 Regression Analyses of Association Between Severity of Anemia During Pregnancy and Severe Maternal Outcomes

	RR (95% CI)
Modified Poisson regression
Crude
Mild anemia	1.90 (1.26–2.88)
Moderate anemia	13.94 (10.88–17.86)
Severe anemia	132.56 (97.36–180.50)
Adjusted
Mild anemia	0.96 (0.62–1.47)
Moderate anemia	4.19 (3.20–5.50)
Severe anemia	22.12 (15.43–31.69)
Multiple pregnancies	1.24 (0.80–1.93)
Referred in from other facility	6.72 (3.93–11.50)
Hemorrhagic disorders	19.56 (15.39–24.85)
Infections	2.77 (1.98–3.88)
Hypertensive disorders	1.07 (0.78–1.47)
Gestational diabetes mellitus	1.21 (0.94–1.56)
Other comorbidities	4.16 (2.90–5.96)
Propensity score weighted regression
Mild anemia	1.00 (1.00–1.00)
Moderate anemia	1.01 (1.01–1.01)
Severe anemia	1.11 (1.07–1.14)

Notes: Maximal model used to develop adjusted RR includes anemia, maternal age, marital status, maternal education, level of hospital, pregnancies, previous births, antenatal examinations, previous cesarean sections, multiple pregnancies, referred in from another facility, hemorrhagic disorders, infections, hypertensive disorders, gestational diabetes mellitus and other comorbidities in the modified Poisson regression analyses. All the above covariates except for hemorrhagic disorders were used for propensity score weighting.