Objectives Many female rheumatoid arthritis (RA) patients attempting to conceive have a time to pregnancy (TTP) of >12 months. During this period RA often cannot be treated optimally. We sought to identify clinical factors associated with prolonged TTP in female RA patients.

Methods In a nationwide prospective cohort study on pregnancy in RA patients (PARA study), women were included preconceptionally or during the first trimester. Cox regression analysis was used to study the association of disease characteristics and medication use with TTP.

Results TTP exceeded 12 months in 42% of 245 patients. Longer TTP was related to age, nulliparity, disease activity (DAS28), and preconception use of non-steroidal anti-inflammatory drugs (NSAIDs) and prednisone. These variables were independently associated with TTP, with HRs for occurrence of pregnancy of 0.96 (95% CI 0.92 to 1.00) per year of age, 0.52 (0.38 to 0.70) for nulliparity, 0.81 (0.71 to 0.93) per point increase in DAS28, 0.66 (0.46 to 0.94) for NSAIDs and 0.61 (0.45 to 0.83) for prednisone use. The impact of prednisone use was dose dependent, with significantly longer TTP when daily dose was >7.5 mg. Smoking, disease duration, rheumatoid factor, anti-citrullinated protein antibodies, past methotrexate use, and preconception sulfasalazine use did not prolong TTP.

Conclusions TTP in RA is longer if patients are older or nulliparous, have higher disease activity, use NSAIDs or use prednisone >7.5 mg daily. Preconception treatment strategies should aim at maximum suppression of disease activity, taking account of possible negative effects of NSAIDs use and higher prednisone doses.