Baseline characteristics by post-onset pregnancy and baseline associations with likelihood of post-onset pregnancy (adjusted for age at symptom onset)
| Cohort characteristics at baseline | Women who had a post-onset pregnancy (N = 72) | Women who did not have a post-onset pregnancy (N = 559) | p Value | OR* of post-onset pregnancy (95% CI) (reference) |
|---|---|---|---|---|
| Age at IP onset, years: median (IQR) | 27.8 (23.1–30.4); n = 72 | 39.0 (33.1–44.0); n = 559 | <0.001† | 0.83 (0.80 to 0.87)‡ (per year increase) |
| Number of live births by baseline: n/N (%) | <0.001† | 0.79 (0.59 to 1.06) (per live birth) | ||
| 0 | 33/72 (45.8) | 106/559 (19.0) | ||
| 1 | 23/72 (31.9) | 84/559 (15.0) | ||
| 2 | 13/72 (18.1) | 229/559 (41.0) | ||
| 3 | 1/72 (1.4) | 103/559 (18.4) | ||
| 4 | 2/72 (2.8) | 28/559 (5.0) | ||
| 5 | – | 9/559 (1.6) | ||
| Taking contraceptive pill at baseline: n/N (%) | 32/72 (44.4) | 102/559 (18.3) | <0.001† | 1.58 (0.88 to 2.85) (vs not taking) |
| Symptom duration, months: median (IQR) | 7.5 (3.5–12.1); n = 72 | 6.9 (3.2–14.8); n = 559 | 0.94 | 0.99 (0.97 to 1.00) (per month increase) |
| Met ACR (1987) criteria for RA16: n/N (%) | 17/72 (23.6) | 199/559 (35.6) | 0.04† | 0.59 (0.31 to 1.13) (vs did not meet) |
| Positive for RF: n/N (%) | 12/61 (19.7) | 122/486 (25.1) | 0.35 | 1.08 (0.51 to 2.29) (vs negative for RF) |
| Ever positive for RF during follow-up: n/N (%) | 19/70 (27) | 215/539 (40) | – | – |
| Positive for ACPA: n (%) | 6/56 (10.7) | 118/463 (25.5) | 0.01† | 0.41 (0.16 to 1.07) (vs negative for ACPA) |
| Ever positive for ACPA during follow-up: n/N (%) | 10/64 (16) | 135/507 (27) | – | – |
| CRP concentration, mg/litre: mean (SD) | 10.0 (17.8); n = 55 | 10.8 (21.4); n = 447 | 0.80 | 0.99 (0.98 to 1.01) (per mg/litre increase) |
| Swollen and tender joint count (51 joints): median (IQR) | 1 (0–4); n = 72 | 2 (0–6); n = 559 | 0.36 | 0.98 (0.93 to 1.03) (per joint increase) |
| DAS28: mean (SD) | 3.5 (1.3); n = 55 | 3.6 (1.3); n = 447 | 0.60 | 0.96 (0.75 to 1.22) (per increase of 1.0) |
| HAQ score: median (IQR) | 0.63 (0.19–1.0); n = 72 | 0.75 (0.25–1.38); n = 551 | 0.10 | 0.66 (0.43 to 1.01) (per increase of 1.0) |
↵* OR, association with likelihood of having a post-onset pregnancy, compared to (reference).
↵† Significant difference (unadjusted).
↵‡ Significant association with likelihood of post-onset pregnancy.
ACPA, anti-cyclic citrullinated peptide antibody; ACR, American College of Rheumatology; CRP, C reactive protein; DAS28, 28-joint Disease Activity Score; HAQ, Health Assessment Questionnaire; RA, rheumatoid arthritis; RF, rheumatoid factor.