Table 1.
The general characteristics of study population in this study.
| General characteristics | Total (n = 16,535,852) | IVF (n = 183,059) | non-IVF (n = 16,352,793) | P-value |
|---|---|---|---|---|
| Geographical area | ||||
| Eastern | 8462641 (51.2) | 101253 (55.3) | 8361388 (51.1) | <0.001 |
| Central | 3852875 (23.3) | 43965 (24.0) | 3808910 (23.3) | <0.001 |
| Western | 4220336 (25.5) | 37841 (20.7) | 4182495 (25.6) | <0.001 |
| Year | ||||
| 2013 | 751997 (4.5) | 5477 (3.0) | 746520 (4.6) | <0.001 |
| 2014 | 1438167 (8.7) | 9791 (5.4) | 1428376 (8.7) | <0.001 |
| 2015 | 1327773 (8) | 13383 (7.3) | 1314390 (8.0) | <0.001 |
| 2016 | 4370506 (26.4) | 41992 (22.9) | 4328514 (26.5) | <0.001 |
| 2017 | 4451031 (26.9) | 47874 (26.2) | 4403157 (26.9) | <0.001 |
| 2018 | 4196378 (25.4) | 64542 (35.3) | 4131836 (25.3) | <0.001 |
| Maternal age at birth, Mean (SD) | 29.20 (4.6) | 32.51 (4.5) | 29.16 (4.6) | <0.001 |
| 20-24 | 2419814 (14.6) | 4859 (2.7) | 2414955 (14.8) | <0.001 |
| 25-29 | 7184983 (43.5) | 43033 (23.5) | 7141950 (43.7) | <0.001 |
| 30-34 | 4641920 (28.1) | 76727 (41.9) | 4565193 (27.9) | <0.001 |
| 35-39 | 1857960 (11.2) | 46330 (25.3) | 1811630 (11.1) | <0.001 |
| 40-44 | 402996 (2.4) | 10990 (6.0) | 392006 (2.4) | <0.001 |
| 45-49 | 28179 (0.2) | 1120 (0.6) | 27059 (0.2) | <0.001 |
| Ethnicity | ||||
| Minority | 1515065 (9.2) | 16366 (8.9) | 1498699 (9.2) | <0.001 |
| Han | 14856494 (89.8) | 165736 (90.5) | 14690758 (89.8) | <0.001 |
| Unknown | 164293 (1.0) | 957 (0.5) | 163336 (1.0) | <0.001 |
| Chronic diseases before pregnancy | ||||
| Chronic hypertension | 133051 (0.8) | 2713 (1.5) | 130338 (0.8) | <0.001 |
| Diabetes | 158200 (1.0) | 3822 (2.1) | 154378 (0.9) | <0.001 |
| Thyroid diseases | 640093 (3.9) | 13441 (7.3) | 626652 (3.8) | <0.001 |
| Anemia | 2589684 (15.7) | 29171 (15.9) | 2560513 (15.7) | 0.0012 |
| Circulatory diseases | 167004 (1.0) | 2665 (1.5) | 164339 (1.0) | <0.001 |
| *Other chronic conditions | 734827 (4.4) | 11226 (6.1) | 723601 (4.4) | <0.001 |
* “Other chronic conditions” included coagulation disorders, kidney diseases, diseases of connective tissues, diseases of respiratory system, and diseases of digestive system.