MMF is teratogenic and needs to be replaced before pregnancy. This change may lead to flares. Our aim was to determine the risk of renal flares in women with LN who switched treatment from MMF to AZA before conception and to evaluate the outcome of their pregnancies.

Medical records of women with LN counselled for pregnancy wish were reviewed. Women receiving treatment with either MMF or AZA (control group), with inactive lupus (SLEDAI ≤ 4) and quiescent LN (serum creatinine <1.5 mg/dl, inactive sediment and proteinuria <1 g/24 h for the preceding 6 months) were eligible for this study.

We identified 54 women [23 treated with MMF (group 1) and 31 treated with AZA (group 2)]. MMF dosage was tapered and subsequently transferred to AZA, which was maintained throughout pregnancy. Three (13%) patients (group 1) vs none (group 2) developed a renal flare 3-6 months after transitioning from MMF to AZA (P = 0.14) before pregnancy ensued. The only parameter with a significant difference in those with flare compared with those without was younger age (median 27 vs 30 years; P = 0.03). Risk for adverse outcome within 48 pregnancies (pre-eclampsia 9%, preterm delivery 20.5%) increased with every milligramme of prednisone dosage [odds ratio (OR) 2.03] and every single unit of SLEDAI score (OR 3.92). Renal flares occurred post-partum in two women. No patient developed worsening of renal function.

Replacing MMF with AZA in patients with quiescent LN for pregnancy planning rarely leads to renal flares. Pregnancy outcome was favourable.