“Pregnancy in adult-onset idiopathic inflammatory myopathy”: Report from a cohort of myositis patients from a single center

Background and purpose

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

Methods

A total of 51 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

A total of 102 pregnancies from 51 patients (41 with dermatomyositis and 10 with polymyositis) were analyzed. A total of 14 pregnancies from 8 patients occurred after disease onset; statistically significant (p = 0.02) 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 patients 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 = 0.71).

Conclusions

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