Table 1.
Maternal characteristics among women with and without an ARD diagnosis in the whole population and the propensity-matched sample.
| Characteristic | Before propensity score matching | Propensity-matched sample | ||||
| No ARD diagnosis n (%) |
Any ARD diagnosis n (%) |
P value | No ARD diagnosis n (%) |
Any ARD diagnosis n (%) |
P value | |
| Sample size | 2 952 913 (99.6) | 10 975 (0.4) | 10 244 (50.0) | 10 244 (50.0) | ||
| Race/ethnicity | ||||||
| White, not Hispanic | 768 872 (26.0) | 4480 (40.8) | <0.001* | 4309 (42.1) | 4309 (42.1) | 1.000 |
| Hispanic | 1 441 577 (48.8) | 3779 (34.4) | 3620 (35.3) | 3620 (35.3) | ||
| Black | 158,030 5.4) | 772 (7.0) | 714 (7.0) | 714 (7.0) | ||
| Asian | 365 761 (12.4) | 971 (8.9) | 931 (9.1) | 931 (9.1) | ||
| Other | 218 673 (7.4) | 973 (8.9) | 670 (6.5) | 670 (6.5) | ||
| Age at delivery | ||||||
| <18 years | 85 632 (2.9) | 85 (0.8) | <0.001* | 78 (0.8) | 78 (0.8) | 1.000 |
| 18–34 years | 2 343 913 (79.4) | 7732 (70.5) | 7286 (71.1) | 7286 (71.1) | ||
| >34 years | 523 257 (17.7) | 3158 (28.8) | 2880 (28.1) | 2880 (28.1) | ||
| Missing | 111 | 0 | 0 | 0 | ||
| Pre-pregnancy body mass index | ||||||
| <18.5 kg/m2 | 143 904 (5.2) | 482 (4.7) | <0.001* | 397 (4.1) | 454 (4.7) | 0.166 |
| 18.5–24.9 kg/m2 | 1 347 265 (48.9) | 4963 (48.0) | 4644 (48.1) | 4660 (48.1) | ||
| 25.0–29.9 kg/m2 | 701 724 (25.5) | 2591 (25.0) | 2399 (24.9) | 2431 (25.1) | ||
| ≥30.0 kg/m2 | 560 763 (20.4) | 2314 (22.4) | 2211 (22.9) | 2142 (22.1) | ||
| Missing | 199 257 | 625 | 593 | 557 | ||
| Mode of delivery | ||||||
| Vaginal | 2 001 137 (68.2) | 6038 (55.5) | <0.001* | 5713 (55.8) | 5713 (55.8) | 1.000 |
| Caesarean | 933 625 (31.8) | 4840 (44.5) | 4531 (44.2) | 4531 (44.2) | ||
| Missing | 18 151 | 97 | 0 | 0 | ||
| Primary insurance enrolment | ||||||
| Private | 1 366 774 (46.4) | 6765 (61.7) | <0.001* | 6362 (62.1) | 6362 (62.1) | 1.000 |
| Medicaid/Medical | 1 426 764 (48.4) | 3675 (33.5) | 3414 (33.3) | 3414 (33.3) | ||
| Self-pay | 59 765 (2.0) | 90 (0.8) | 71 (0.7) | 71 (0.7) | ||
| Other | 94 846 (3.2) | 432 (3.4) | 397 (3.9) | 397 (3.9) | ||
| Missing | 4764 | 13 | 0 | 0 | ||
| Maternal education | ||||||
| <12 years | 707 492 (24.9) | 1315 (12.5) | <0.001* | 1257 (12.3) | 1257 (12.3) | 1.000 |
| 12 years | 755 504 (26.6) | 2342 (22.3) | 2255 (22.0) | 2255 (22.0) | ||
| >12 years | 1 380 922 (48.6) | 6856 (65.2) | 6732 (65.7) | 6732 (65.7) | ||
| Missing | 108 995 | 462 | 0 | 0 | ||
| Smoked during pregnancy | 134 019 (4.5) | 663 (6.0) | <0.001* | 559 (5.5) | 559 (5.5) | 1.000 |
| Drug/alcohol use during pregnancy | 56 888 (1.9) | 506 (4.6) | <0.001* | 405 (4.0) | 405 (4.0) | 1.000 |
| Previous preterm birth | 19 798 (0.7) | 234 (2.1) | <0.001* | 188 (1.8) | 188 (1.8) | 1.000 |
| Thyroid disorder | 58 690 (2.0) | 897 (8.2) | <0.001* | 772 (7.5) | 772 (7.5) | 1.000 |
| Asthma | 118 695 (4.0) | 1100 (10.0) | <0.001* | 969 (9.5) | 969 (9.5) | 1.000 |
| Diabetes | 277 977 (9.4) | 1351 (12.3) | <0.001* | 1194 (11.7) | 1194 (11.7) | 1.000 |
| Hypertensive disorder | 210 825 (7.1) | 1765 (16.1) | <0.001* | 1578 (15.4) | 1578 (15.4) | 1.000 |
| Year of birth | ||||||
| 2007 | 529 945 (18.0) | 1494 (13.6) | <0.001* | 1392 (13.6) | 1392 (13.6) | 1.000 |
| 2008 | 516 603 (17.5) | 1697 (15.5) | 1571 (15.3) | 1571 (15.3) | ||
| 2009 | 492 401 (16.7) | 1841 (16.8) | 1713 (16.7) | 1713 (16.7) | ||
| 2010 | 476 945 (16.2) | 1861 (17.0) | 1755 (17.1) | 1755 (17.1) | ||
| 2011 | 469 026 (15.9) | 1964 (17.9) | 1843 (18.0) | 1843 (18.0) | ||
| 2012 | 467 993 (15.9) | 2118 (19.3) | 1970 (19.2) | 1970 (19.2) | ||
P values were calculated using Pearson’s χ2 test.
*P<0.05.
ARD, autoimmune rheumatic disease.