Table 1. Maternal Baseline Characteristics by Anemia Status During Pregnancya.
| Characteristic | Patients, No. (%) | ||||||
|---|---|---|---|---|---|---|---|
| No anemia (n = 15 578 790) | Anemia | Total (N = 18 948 443) | |||||
| Mild (n = 1 713 722) | Moderate (n = 497 363) | Severe (n = 40 458) | Unknown severity (n = 1 118 110) | All (n = 3 369 653) | |||
| Region | |||||||
| Eastern China | 7 810 807 (50.14) | 1 084 724 (63.30) | 256 672 (51.61) | 16 717 (41.32) | 500 471 (44.76) | 1 858 584 (55.16) | 9 669 391 (51.03) |
| Central China | 3 786 454 (24.31) | 242 273 (14.14) | 104 682 (21.05) | 4927 (12.18) | 221 113 (19.78) | 572 995 (17.00) | 4 359 449 (23.01) |
| Western China | 3 981 529 (25.56) | 386 725 (22.57) | 136 009 (27.35) | 18 814 (46.50) | 396 526 (35.46) | 938 074 (27.84) | 4 919 603 (25.96) |
| Year | |||||||
| 2016 | 4 132 573 (26.53) | 400 214 (23.35) | 56 021 (11.26) | 13 594 (33.60) | 249 316 (22.30) | 719 145 (21.34) | 4 851 718 (25.60) |
| 2017 | 4 098 427 (26.31) | 452 813 (26.42) | 77 360 (15.55) | 9488 (23.45) | 280 092 (25.05) | 819 753 (24.33) | 4 918 180 (25.96) |
| 2018 | 3 775 312 (24.23) | 452 237 (26.39) | 100 164 (20.14) | 6707 (16.58) | 283 773 (25.38) | 842 881 (25.01) | 4 618 193 (24.37) |
| 2019 | 3 572 478 (22.93) | 408 458 (23.83) | 263 818 (53.04) | 10 669 (26.37) | 304 929 (27.27) | 987 874 (29.32) | 4 560 352 (24.07) |
| Age, mean (SD), y | 29.42 (4.89) | 29.46 (5.13) | 29.51 (5.35) | 29.46 (6.11) | 29.43 (5.19) | 29.46 (5.19) | 29.42 (4.87) |
| Ethnicity | |||||||
| Han | 14 340 366 (92.05) | 1 566 686 (91.42) | 449 605 (90.40) | 27 477 (67.91) | 1 002 603 (89.67) | 3 046 371 (90.41) | 17 386 737 (91.76) |
| Otherb | 1 083 293 (6.95) | 136 694 (7.98) | 43 485 (8.74) | 12 848 (31.76) | 99 462 (8.90) | 292 489 (8.68) | 1 375 782 (7.26) |
| Unknown | 155 131 (1.00) | 10 342 (0.60) | 4273 (0.86) | 133 (0.33) | 16 045 (1.44) | 30 793 (0.91) | 185 924 (0.98) |
| Marital status | |||||||
| Married | 14 586 004 (93.63) | 1 621 127 (94.60) | 464 826 (93.46) | 30 469 (75.31) | 1 061 613 (94.95) | 3 178 035 (94.31) | 17 764 039 (93.75) |
| Unmarried | 483 754 (3.11) | 58 611 (3.42) | 19 689 (3.96) | 1652 (4.08) | 31 931 (2.86) | 111 883 (3.32) | 595 637 (3.14) |
| Widowed or divorced | 95 807 (0.61) | 6802 (0.40) | 1879 (0.38) | 135 (0.33) | 2782 (0.25) | 11 598 (0.34) | 107 405 (0.57) |
| Unknown | 413 225 (2.65) | 27 182 (1.59) | 10 969 (2.21) | 8202 (20.27) | 21 784 (1.95) | 68 137 (2.02) | 481 362 (2.54) |
| Medical insurance | |||||||
| Yes | 10 829 503 (69.51) | 1 116 359 (65.14) | 311 216 (62.57) | 19 235 (47.54) | 778 018 (69.58) | 2 224 828 (66.03) | 13 054 331 (68.89) |
| No | 4 743 215 (30.45) | 597 115 (34.84) | 186 128 (37.42) | 21 221 (52.45) | 339 960 (30.40) | 1 144 424 (33.96) | 5 887 639 (31.07) |
| Unknown | 6072 (0.04) | 248 (0.01) | 19 (0.00) | 2 (0.00) | 132 (0.01) | 401 (0.01) | 6473 (0.03) |
| Maternal complications during pregnancy | |||||||
| In vitro fertilization | 295 701 (1.90) | 36 613 (2.14) | 16 825 (3.38) | 993 (2.45) | 22 525 (2.01) | 76 956 (2.28) | 372 657 (1.97) |
| Multiple pregnancies | 486 602 (3.12) | 82 407 (4.81) | 34 762 (6.99) | 2552 (6.31) | 49 169 (4.40) | 168 890 (5.01) | 655 492 (3.46) |
| Hypertension disorders | 889 798 (5.71) | 94 068 (5.49) | 34 648 (6.97) | 5010 (12.38) | 72 220 (6.46) | 205 946 (6.11) | 1 095 744 (5.78) |
| Diabetes | 2 020 919 (12.97) | 220 997 (12.90) | 64 098 (12.89) | 5372 (13.28) | 148 103 (13.25) | 438 570 (13.02) | 2 459 489 (12.98) |
| Thyroid diseases | 678 072 (4.35) | 98 343 (5.74) | 28 076 (5.64) | 2004 (4.95) | 68 203 (6.10) | 196 626 (5.84) | 874 698 (4.62) |
| Circulatory diseases | 171 453 (1.10) | 26 897 (1.57) | 11 007 (2.21) | 1172 (2.90) | 17 160 (1.53) | 56 236 (1.67) | 227 689 (1.20) |
| Urinary diseases | 79 868 (0.51) | 18 734 (1.09) | 6911 (1.39) | 628 (1.55) | 8136 (0.73) | 34 409 (1.02) | 114 277 (0.60) |
| Respiratory diseases | 152 073 (0.98) | 29 136 (1.70) | 10 651 (2.14) | 1381 (3.41) | 17 463 (1.56) | 58 631 (1.74) | 210 704 (1.11) |
| Digestive diseases | 340 055 (2.18) | 56 105 (3.27) | 21 528 (4.33) | 1975 (4.88) | 42 420 (3.79) | 122 028 (3.62) | 462 083 (2.44) |
| Coagulation disorders | 30 547 (0.20) | 26 225 (1.53) | 19 118 (3.84) | 1493 (3.69) | 154 849 (13.85) | 201 685 (5.99) | 232 232 (1.23) |
| Scarred uterus | 3 281 344 (21.06) | 445 916 (26.02) | 136 249 (27.39) | 9524 (23.54) | 280 909 (25.12) | 872 598 (25.90) | 4 153 942 (21.92) |
| Placenta previa | 280 134 (1.80) | 45 473 (2.65) | 22 864 (4.60) | 2370 (5.86) | 32 902 (2.94) | 103 609 (3.07) | 383 743 (2.03) |
| Placenta accreta spectrum | 326 700 (2.10) | 43 897 (2.56) | 22 257 (4.48) | 2112 (5.22) | 37 158 (3.32) | 105 424 (3.13) | 432 124 (2.28) |
| Antepartum hemorrhage | 12 653 (0.08) | 1769 (0.10) | 752 (0.15) | 186 (0.46) | 1558 (0.14) | 4265 (0.13) | 16 918 (0.09) |
| Intrauterine infection | 152 691 (0.98) | 41 829 (2.44) | 13 903 (2.80) | 1722 (4.26) | 11 878 (1.06) | 69 332 (2.06) | 222 023 (1.17) |
| Abnormal amniotic fluid | 963 679 (6.19) | 141 080 (8.23) | 37 773 (7.59) | 2156 (5.33) | 57 201 (5.12) | 238 210 (7.07) | 1 201 889 (6.34) |
| Cervical incompetence | 438 392 (2.81) | 17 608 (1.03) | 4609 (0.93) | 292 (0.72) | 18 195 (1.63) | 40 704 (1.21) | 479 096 (2.53) |
| Abnormal placenta | 328 430 (2.11) | 49 367 (2.88) | 17 559 (3.53) | 1124 (2.78) | 27 091 (2.42) | 95 141 (2.82) | 423 571 (2.24) |
SI conversion factor: To convert hemoglobin concentration to grams per deciliter, divide by 10.0.
a
No anemia was defined as a hemoglobin concentration of 110 g/L or greater; mild anemia, 100 to 109 g/L; moderate anemia, 70 to 99 g/L; severe anemia, less than 70 g/L.
b
Because there are more than 50 ethnic groups in China, other groups are not listed individually.