Background Idiopathic inflammatory myopathies (IIM) are systemic diseases, characterized by the presence of an inflammatory muscle infiltrate. Although more frequent in women, its relationship with pregnancy has not been extensively studied.

Objectives Our goal was to analyze the interaction between pregnancy and myositis in a cohort of IIM women from a single center.

Methods Fifty-one patients from a historical cohort of IIM diagnosed between 1983 and 2013 were interviewed with a specific questionnaire. Comparisons between pregnancies occurring before and after the onset of the disease were performed using generalized mixed-effect models with normal and binomial distributions adjusted for confounding factors and clustering.

Results One-hundred and two pregnancies from 51 patients (41 dermatomyositis [DM] and 10 polymyositis [PM]) were analyzed. Fourteen (13.7%) pregnancies from 8 patients (5 DM, 3 PM) occurred after disease onset; clinical improvement during gestation was evident in 7 pregnancies (4 patients), 5 of them (from 2 patients) experienced a relapse of IIM symptoms afterwards, while in the rest there was no influence of pregnancy on the disease. No disease flare associated with pregnancy was observed. Two (3.9%) patients (2 DM) were diagnosed within the first 6 months after delivery and none during pregnancy. No evidence was found to support pregnancy as a trigger for myopathy (p=0.10).

Conclusions Pregnancy does not seem to carry a worse prognosis for the mother nor for the fetus in patients with IIM; on the contrary, near half of the patients in our series improved clinically when they became pregnant, being common a relapse of IIM symptoms afterwards. Pregnancy does not appear to be a trigger for IIM.

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Acknowledgements We thank Dr. Pari Basharat and Dr. Arash Lahoutiharahdashti for their critical review of the project.

Disclosure of Interest None declared

DOI 10.1136/annrheumdis-2014-eular.1571