Table 1.
Baseline characteristics of study population.
| Characteristics * | Overall (N = 503,491) |
No RA or JIA (N = 501,285) |
RA and JIA (N = 2206) |
|---|---|---|---|
| N (%) | N (%) | N (%) | |
| Age (years) | |||
| <25 | 76,972 (15.3) | 76,608 (15.3) | 364 (16.5) |
| 25–29 | 175,596 (34.9) | 174,943 (34.9) | 653 (29.6) |
| 30–34 | 166,247 (33.0) | 165,536 (33.0) | 711 (32.2) |
| ≥35 | 84,676 (16.8) | 84,198 (16.8) | 478 (21.7) |
| Race | |||
| Afro-Caribbean | 5785 (1.2) | 5770 (1.2) | 15 (0.7) |
| Asian | 17,230 (3.5) | 17,189 (3.5) | 41 (1.9) |
| Caucasian | 457,274 (93.6) | 455,221 (93.6) | 2053 (96.1) |
| Other ± | 8436 (1.7) | 8409 (1.7) | 27 (1.3) |
| Pre-gestational Body Mass Index (kg/m2) | |||
| <18.5 | 31,927 (6.5) | 31,798 (6.5) | 129 (6.1) |
| 18.5–24 | 287,290 (58.8) | 286,083 (58.8) | 1207 (56.7) |
| 25–29 | 106,537 (21.8) | 105,022 (21.8) | 515 (24.2) |
| ≥30 | 62,884 (12.9) | 62,607 (12.9) | 277 (13.0) |
| Smoking status during pregnancy | |||
| Former | 7642 (1.5) | 7606 (1.5) | 36 (1.7) |
| Non-smoker | 442,531 (89.4) | 440,591 (89.4) | 1940 (89.8) |
| Smoker | 44,832 (9.1) | 44,648 (9.0) | 184 (8.5) |
| Income status | |||
| In school | 33,471 (6.7) | 33,317 (6.6) | 154 (7.0) |
| Employed | 351,448 (69.8) | 350,043 (69.8) | 1405 (63.7) |
| Transfer payment ¶ | 111,390 (22.1) | 110,811 (22.1) | 579 (26.2) |
| Early retirement | 3251 (0.6) | 3191 (0.6) | 60 (2.7) |
| Unemployed | 3699 (0.7) | 3691 (0.7) | 8 (0.4) |
| Parity | |||
| Nulliparous | 180,161 (35.8) | 179,317 (35.8) | 844 (38.3) |
| Multiparous | 323,324 (64.2) | 321,962 (64.2) | 1362 (61.7) |
| Co-morbidities | |||
| Pregestational hypertension | 4472 (0.9) | 4431 (0.9) | 41 (1.9) |
| Gestational hypertension | 10,856 (2.2) | 10,778 (2.2) | 68 (3.1) |
| Pre-eclampsia/eclampsia | 19,814 (3.9) | 19,707 (3.9) | 107 (4.9) |
| Pregestational diabetes | 3611 (0.7) | 3585 (0.7) | 26 (1.2) |
| Gestational diabetes | 18,031 (3.6) | 17,951 (3.6) | 80 (3.6) |
| Birth-related characteristics | |||
| Pregnancy Outcome | |||
| Stillborn | 1049 (0.2%) | 1045 (0.2%) | 4 (0.2%) |
| Gestational Age at Birth (weeks) | |||
| <32 | 3606 (0.7%) | 3587 (0.7%) | 19 (0.8%) |
| ≥32 to <37 | 20,488 (4.1%) | 20,361 (4.1%) | 127 (5.8%) |
| ≥37 to <42 | 464,218 (92.2%) | 462,218 (92.2%) | 2000 (90.7%) |
| ≥42 | 15,179 (3.0%) | 15,119 (3.0%) | 60 (2.7%) |
| Mode of Delivery | |||
| Vaginal delivery | 402,700 (80.0%) | 401,056 (80.0%) | 1644 (74.5%) |
| Cesarean section | 100,791 (20.0%) | 100,229 (20.0%) | 562 (25.5%) |
* Variables contain missing values. ¶ Transfer payment: Temporary income for individuals administered by employer or government due to a health condition. ± Identify as multiracial.