Association of blood parameters in early pregnancy with anemia during late pregnancy: a multicenter cohort study in China

Figures & data

Figure 1. Study flow chart. SF: serum ferritin.

Table 1. Demographic characteristics.

Number of women	1566
Ethnicity
Han	1529 (97.6%)
Others	37 (2.4%)
Education status
Primary school	6 (0.4%)
Junior high school	60 (3.8%)
Senior high school	184 (11.7%)
Undergraduate college or above	1316 (84.1%)
Household registration
City dweller	1118 (71.4%)
Farmer	448 (28.6%)
Annual income (China Yuan, CNY)
<200,000	1006 (64.0%)
≥200,000	560 (36.0%)
Nulliparous women	1058 (67.6%)
Pre-pregnancy BMI, kg/m^2	21.2 (15.2–37.3)
GWs at delivery	39.1 (36.1–42.0)
Vaginal delivery	825 (52.7%)
Cesarean section	741 (47.3%)
Birthweight, g	3324 (1690–5980)
Iron supplementation after the first 3 months of pregnancy	1243 (79.4%)
Duration of iron supplementation
Never	323 (20.6%)
≤3 months	514 (32.8%)
>3 months	729 (46.6%)
Duration of folic acid supplementation
Never	241 (15.4%)
≤3 months	495 (31.6%)
>3 months	830 (53.0%)
GW at blood sampling
First trimester	11.3 (3.2–13.6)
Second trimester	23.4 (14–27.6)
Third trimester	33.0 (28–41.1)
Anemia in the second trimester (hemoglobin level <105 g/L)	63 (4.0%)
Anemia in the third trimester	124 (7.9%)

Data are presented as mean (range) or percentage. BMI: body mass index; GW: gestational week.

Table 2. Clinical data and blood parameters during pregnancy.

Clinical data	First trimester	Second trimester	Third trimester
Maternal body weight, kg	54.8 ± 7.9	56.8 ± 7.9^a	63.6 ± 7.8^a
Systolic blood pressure, mmHg	112 ± 10	113 ± 10^a	114 ± 10^a
Diastolic blood pressure, mmHg	70 ± 9	68 ± 8^a	67 ± 8^a
Weight gain in pregnancy, kg	0.8 ± 3.6	2.0 ± 2.6^a	6.8 ± 3.8^a
Blood data
PLT count, ×10^9/L	212 (179, 247)	191 (160, 225)^a	177 (149, 210)^a
Hemoglobin level, g/L	128 (122, 134)	118 (112, 123)^a	121 (115, 128)^a
<110 g/L	0	177 (11.3%)	124 (7.9%)^b
<105 g/L	0	63 (4.0 %)	58 (3.7%)
Hematocrit level, %	37.5 (35.8,39.0)	34.8 (33.1, 36.4)^a	35.8 (33.9, 37.6)^a
RBC count, ×10^12/L	4.2 (4.0, 4.4)	3.7 (3.5, 4.0)^a	3.8 (3.6, 4.1)^a
MCV, fL	89.6 (87.0, 92.2)	93.8 (91.1, 96.5)^a	94.0 (91.2, 97.0)^a
MCH, pg	30.7 (29.8, 31.6)	31.8 (30.7, 32.8)^a	31.9 (30.7, 33.0)^a
MCHC, g/L	342 (335, 349)	337 (332, 343)^a	338 (332, 344)^a
Ferritin level, µg/L	63.3 (36.9, 103.7)	23.3 (15.0, 37.0)^a	20.2 (12.2, 27.6)^a
<30 µg/L	280 (17.9%)	1033 (66.0%)^a	1236 (78.9%)^a
<20 µg/L	132 (8.4%)	590 (37.7%)^a	741 (47.3%)^a
IDA	0	80 (5.1%)	89 (5.7%)

Clinical data are presented as mean ± standard deviation. Blood data are presented as median (25^th percentile, 75^th percentile). ^a p < 0.05 versus baseline value of the same group determined in the first trimester. ^b: among 124 women with an Hb level <110 g/L in the third trimester, 47 women had an Hb level <105 in the second trimester; PLT: platelet; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; IDA: iron deficiency anemia.

Table 3. Demographic characteristics and blood variables of women with and without anemia.

Clinical Data	Non-Anemia	Anemia	χ^2/z score	P-value
Number of women	1442	124
Ethnicity
Han	1409 (92.2%)	120 (7.8%)	0.12	0.725
Others	33 (89.2%)	4 (10.8%)
Education status
Primary school	3 (50%)	3 (50%)	9.41	0.020
Junior high school	57 (95%)	3 (5%)
Senior high school	168 (91.3%)	16 (8.7%)
Undergraduate college or above	1214 (92.2%)	102 (7.8%)
Household registration
City dweller	1031 (92.2%)	87 (7.8%)	0.10	0.752
Farmer	411 (91.7%)	37 (8.3%)
Annual income (CNY)
<200,000	925 (91.9%)	81 (8.1%)	0.07	0.793
≥200,000	517 (92.3%)	43 (7.7%)
Nulliparous women
Yes	982 (92.8%)	76 (7.2%)	2.42	0.120
No	460 (90.6%)	48 (9.4%)
Pre-pregnancy BMI, kg/m^2	20.7 (3.4)	20.5 (3.9)	0.99	0.323
Gestational weeks at delivery	39.2 (1.5)	39.2 (1.0)	0.47	0.635
Delivery mode
Vaginal	767 (93%)	58 (7%)	1.89	0.170
Cesarean	675 (91.1%)	66 (8.9%)
Birthweight, g	3300 (550)	3395 (503)	1.76	0.078
Anemia in the second trimester
Yes	98 (55.4%)	79 (44.6%)	368.90	<0.001
No	1344 (96.8%)	45 (3.2%)
Iron supplementation after the first 3 months of pregnancy
Yes	1149 (92.4%)	95 (7.6%)	0.66	0.417
No	293 (91%)	29 (9%)
Duration of iron supplementation
Never	294 (91%)	29 (9%)	2.11	0.348
≤3 months	469 (91.2%)	45 (8.8%)
>3 months	679 (93.1%)	50 (6.9%)
Duration of folic acid supplementation
Never	223 (92.5%)	18 (7.5%)	2.50	0.286
≤3 months	448 (90.5%)	47 (9.5%)
>3 months	771 (92.9%)	59 (7.1%)
Blood data
PLT count, ×10^9/L	213 (70)	207 (62.1)	1.52	0.128
Hemoglobin level, g/L	128 (11)	122 (9)	7.48	<0.001
Hematocrit level, %	37.6 (3.3)	36.2 (2.8)	6.09	<0.001
RBC count, ×10^12/L	4.2 (0.4)	4.1 (0.4)	3.85	<0.001
MCV, fL	89.7 (5.2)	89.2 (5.1)	1.10	0.274
MCH, pg	30.7 (1.9)	30.5 (1.9)	1.87	0.061
MCHC, g/L	342 (14)	340 (14)	2.58	<0.001
Ferritin level, µg/L	63.9 (67.5)	58.4 (62.9)	1.49	0.137

Clinical data and blood data are presented as median (interquartile range). BMI: body mass index; PLT: platelet; RBC: red blood cell; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration.

Table 4. Screening characteristics of optimal cutoff values suggested by ROC curves for predicting anemia (third trimester).

Blood Variable	AUC	Cutoff Value	Sensitivity	Specificity
Hemoglobin level, g/L	0.70^a	128	82.3%	49.6%
PLT count, ×10^9/L	0.54	156	19.4%	88.6%
RBC count, ×10^12/L	0.60^a	4.1	62.1%	57.6%
Hematocrit level, %	0.67^a	37.3	71.8%	53.4%
MCV, fL	0.53	85.1	19.4%	87.1%
MCH, pg	0.55	28.9	21.0%	88.3%
MCHC, g/L	0.57^a	343	71.0%	42.9%
Ferritin level, µg/L	0.54	75.6	66.9%	42.5%

^a p < 0.05. AUC: area under the curve; PLT: platelet; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; ROC: receiver operating characteristic.

Table 5. Screening characteristics of optimal cutoff values suggested by ROC curves for predicting IDA (third trimester).

Blood Variable	AUC	Cutoff Value	Sensitivity	Specificity
Hemoglobin level, g/L	0.71^a	124	66.3%	66.4%
PLT count, ×10^9/L	0.54	207	55.1%	53.8%
RBC count, ×10^12/L	0.62^a	3.9	42.7%	78.8%
Hematocrit level, %	0.67^a	37.0	71.9%	56.9%
MCV, fL	0.52	90	50.6%	55.9%
MCH, pg	0.55	31.4	76.4%	32.2%
MCHC, g/L	0.56	343	69.7%	42.5%
Ferritin, µg/L	0.60^a	75.6	76.4%	42.9%

^a p < 0.05. IDA: iron deficiency anemia; AUC: area under the curve; PLT: platelet; MCV: mean corpuscular volume; MCH: mean corpuscular hemoglobin; MCHC: mean corpuscular hemoglobin concentration; ROC: receiver operating characteristic.

Data availability statement

The data presented in this study are available upon request from the corresponding author. The data are not publicly available to protect patients’ privacy.