Table 4

Relative incidence rate 0–24 months versus 25–48 months post partum by type of arthritis and birth order

IRR (SE)95% CIp Value
RA
Diagnosis after all pregnancies1.73 (0.39)1.11 to 2.700.01
Diagnosis after 1st pregnancy2.23 (0.84)1.06 to 4.700.03
Diagnosis after 2nd and additional pregnancies1.48 (0.42)0.84 to 2.580.17
OCA
Diagnosis after all pregnancies1.05 (0.30)0.59 to 1.840.86
Diagnosis after first pregnancy1.87 (0.97)0.67 to 5.210.22
Diagnosis after second and additional pregnancies0.77 (0.27)0.38 to 1.550.47
RA + OCA
Diagnosis after all pregnancies1.44 (0.25)1.02 to 2.040.04
Diagnosis after first pregnancy2.10 (0.64)1.15 to 3.840.01
Diagnosis after second and additional pregnancies1.16 (0.25)0.75 to 1.780.50

  • CI, confidence interval; IRR, incidence rate ratio; OCA, other chronic arthritides; RA, rheumatoid arthritis; SE, standard error.