Baseline characteristics of the study population at the date of conception
| Variables | All pregnancies (n=5728) | Delivery (n=4576) | APO (n=1152) | P value |
| Age, years | 33.7±4.1 | 33.3±3.8 | 33.7±4.5 | <0.001 |
| Type of insurance | 0.011 | |||
| National Health Insurance | 5679 (99.1) | 4544 (99.3) | 1135 (98.5) | |
| Medicaid | 49 (0.9) | 32 (0.7) | 17 (1.5) | |
| Type of institution* | <0.001 | |||
| Tertiary referral hospital | 2408 (42.1) | 1958 (42.8) | 450 (39.1) | |
| General hospital | 1281 (22.4) | 1056 (23.1) | 225 (19.5) | |
| Community hospital/clinic | 2039 (35.6) | 1562 (34.1) | 477 (41.4) | |
| Income (n=5672, 4530, 1142) | 0.03 | |||
| First quartile | 942 (16.4) | 723 (15.8) | 219 (19.0) | |
| Second quartile | 1318 (23.0) | 1081 (23.6) | 237 (20.6) | |
| Third quartile | 2123 (37.1) | 1708 (37.3) | 415 (36.0) | |
| Fourth quartile | 1289 (22.5) | 1018 (22.2) | 271 (23.5) | |
| Seopositivity | 0.798 | |||
| Seropositive | 2616 (45.7) | 2086 (45.6) | 530 (46.0) | |
| Seronegative | 3112 (54.3) | 2490 (54.4) | 622 (54.0) | |
| Period from RA diagnosis to pregnancy, years | 3.2±2.3 | 3.2±2.3 | 3.3±2.4 | 0.539 |
| Type of APO | N/A | |||
| Abortion | 1122 (97.4) | |||
| Stillbirth | 30 (2.6) | |||
| Comorbidities† | ||||
| Peripheral vascular disease | 160 (2.8) | 131 (2.9) | 29 (2.5) | 0.534 |
| Cerebrovascular disease | 34 (0.6) | 20 (0.4) | 14 (1.2) | 0.002 |
| Chronic pulmonary disease | 1348 (23.5) | 1046 (22.9) | 302 (26.2) | 0.014 |
| Peptic ulcer disease | 1121 (19.6) | 885 (19.3) | 236 (20.5) | 0.358 |
| Mild liver disease | 779 (13.6) | 617 (13.5) | 162 (14.1) | 0.584 |
| Diabetes mellitus without complication | 161 (2.8) | 112 (2.4) | 49 (4.3) | <0.001 |
| Diabetes mellitus with complication | 19 (0.3) | 10 (0.2) | 9 (0.8) | 0.003 |
| Any malignancy | 85 (1.5) | 64 (1.4) | 21 (1.8) | 0.282 |
| CCI score | 0.6±0.9 | 0.6±0.9 | 0.6±0.9 | 0.062 |
| Healthcare utilisation† | ||||
| Hospitalisation | 1174 (20.5) | 914 (20.0) | 259 (22.5) | 0.062 |
| Rheumatologist visits | 2077 (36.3) | 1654 (36.1) | 423 (36.7) | 0.542 |
| Emergency department visits | 842 (14.7) | 658 (14.4) | 184 (16.0) | 0.172 |
| Medication† | ||||
| Not used any DMARDs | 3256 (56.8) | 2620 (57.3) | 636 (55.2) | 0.21 |
| Conventional synthetic DMARDs | ||||
| Methotrexate | 1011 (17.7) | 784 (17.1) | 227 (19.7) | 0.041 |
| Leflunomide | 159 (2.8) | 112 (2.5) | 47 (4.1) | 0.003 |
| Hydroxychloroquine | 1660 (29.0) | 1318 (28.8) | 342 (29.7) | 0.554 |
| Sulfasalazine | 807 (14.1) | 673 (14.7) | 134 (11.6) | 0.007 |
| Tacrolimus | 173 (3.0) | 132 (2.9) | 41 (3.6) | 0.232 |
| Targeted therapies | 217 (3.8) | 168 (3.7) | 49 (4.3) | 0.355 |
Data are presented as numbers with percentages (%) or mean±SD.
*The institution of claims for RA closest to the conception date.
†Data within a year before the conception date were used.
APO, adverse pregnancy outcome; CCI, Charlson Comorbidity Index; DMARD, disease-modifying antirheumatic drug; N/A, not applicable; RA, rheumatoid arthritis.