Anemia and iron deficiency are the most common pathologies in pregnancy and associated with adverse pregnancy outcome. As patients with rheumatic diseases are also at high risk for anemia, we aimed to investigate the frequency of anemia and iron deficiency during pregnancy in this group and whether anemia is a risk factor for adverse maternal or child outcome.

We analyzed 368 pregnancies from a German registry for pregnancies in patients with rheumatic diseases (TURIRE) from 2014–2022. Anemia and iron deficiency were defined according to the World Health Organization. Main outcome measures were prevalence of anemia, iron deficiency, and adverse outcomes.

From the 368 patients 61% were diagnosed with a connective tissue disease, 16% with rheumatoid arthritis or juvenile idiopathic arthritis, 14% with spondyloarthritis, 3% with vasculitis and 7% with other. Prevalence of anemia/iron deficiency was 18%/28% in the first, 27%/51% in the second and 33%/62% in the third trimester. Low hemoglobin levels (OR 0.52) or iron deficiency (OR 0.86) had a negative impact on child outcome. However, lower hemoglobin levels were associated with a lower risk for maternal complications (OR 1.47).

Prevalence of anemia and iron deficiency is high in pregnant women with rheumatic diseases. Compared to previously published cohorts of the general population from different countries, the prevalence of anemia and iron deficiency is distinctly higher. Furthermore, patients with rheumatic diseases already start with impaired iron storage and/or hemoglobin levels. Thus, iron supplementation should be initiated early on in this vulnerable in this patient group.