Table 1 Basic characteristics of the participants among 30–36 months old
| Â | Before COVID-19 pandemic (2018.04-2019.12) | During COVID-19 pandemic (2020.04-2021.12) | P-value |
|---|---|---|---|
N(%) | N(%) | ||
Total | 568,495 | 512,388 | Â |
Age(continuous) | 34.45 ± 2.20 | 35.34 ± 2.51 | < 0.0001 |
Preterm birth or LBW | Â | Â | Â |
 Yes | 26,585 (4.68) | 48,149 (9.4) | < 0.0001 |
 No | 541,910 (95.32) | 464,239 (90.6) | |
Sex | Â | Â | Â |
 Boys | 291,337 (51.25) | 262,957 (51.32) | 0.449 |
 Girls | 277,158 (48.75) | 249,431 (48.68) | |
Types of the insured a | Â | Â | Â |
 Medicaid | 5,993 (1.05) | 4,942 (0.96) | < 0.0001 |
 Non-Medicaid | 562,502 (98.95) | 507,446 (99.04) | |
Disability | Â | Â | Â |
 None | 567,042 (99.74) | 510,808 (99.69) | < 0.0001 |
 Yes (Mild or Severe) | 1,453 (0.26) | 1,580 (0.31) | |
Number of pediatricians per population of children | Â | Â | Â |
 None | 11,858 (2.09) | 11,032 (2.15) | < 0.0001 |
 Under mean | 270,451 (47.57) | 234,100 (45.69) | |
 Mean and over | 286,186 (50.34) | 267,256 (52.16) | |
Region | Â | Â | Â |
 Urban | 240,852 (42.37) | 211,700 (41.32) | < 0.0001 |
 Rural | 327,643 (57.63) | 300,688 (58.68) | |
Delayed visit | Â | Â | Â |
 No | 465,405 (81.87) | 340,555 (66.46) | 0.0001 |
 Yes | 103,090 (18.13) | 171,833 (33.54) | |
Section type of survey | Â | Â | Â |
 For 30–32 months | 159,372 (28.03) | 105,735 (20.64) | < 0.0001 |
 For 33–35 months | 229,642 (40.39) | 176,476 (34.44) | |
For 36–41 months | 179,481 (31.57) | 230,177 (44.92) | |
Mother’s age group |  |  |  |
 20–29 | 41,273 (7.26) | 33,349 (6.51) | < 0.0001 |
 30–39 | 366,147 (64.41) | 300,841 (58.71) | |
 40 and over | 64,026 (11.26) | 73,441 (14.33) | |
 Unknown | 97,049 (17.07) | 104,757 (20.44) |  |
Mother’s nationality |  |  |  |
 Korea | 456,407 (80.28) | 391,861 (76.48) | < 0.0001 |
 Foreign | 17,387 (3.06) | 18,183 (3.55) | |
 Unknown | 94,701 (16.66) | 102,344 (19.97) |