Background/Purpose: Idiopathic inflammatory myopathies (IIM) are rare autoimmune conditions which cause multi-organ inflammation, particularly in the skin, lungs, and muscles. It is known that many autoimmune conditions affect a women’s ability to become pregnant and may lead to adverse pregnancy outcomes. Studying pregnancy within IIM has been difficult due to limited cases, yet there is increasing evidence that women with IIM have increased risk of pregnancy adverse outcomes, including pre-eclampsia and low birth weight. However, few studies have evaluated the spectrum of pregnancy outcomes in IIM or compared how these outcomes compare to the general population. Our aim was to evaluate the rate of term pregnancies, preterm pregnancies, abortions, and living children in women with a history of IIM and to compare these with a sample of American women.

Methods: The Montefiore Medical Center Myositis registry was created from patients that met 2017 EULAR/ACR classification criteria for IIM. Demographics, including age, race, ethnicity were documented. IIM subtype and date of diagnosis were also recorded. Patients who did not identify as female and lacked an obstetrics history recorded by a physician were excluded. Pregnancy outcomes, including number of term and preterm pregnancies, abortions, and living children were recorded. A preterm birth was defined as < 37 while term birth was considered >37 weeks. Abortions were further classified into elective, spontaneous, therapeutic, ectopic, or reason unknown. These same pregnancy outcomes were extracted from Section B of the CDC’s 2017-2019 National Survey of Family Group for comparison.

Results: Of 153 patients with IIM, 86 of them were female patients with an obstetrics history. The mean age of IIM diagnosis was 51.7 years old, and majority of women were of Latinx ethnicity (Table 1). There were a total number of 224 pregnancies; 185 were live births with 6 (3%) preterm births.The average number of live births was 2.13 per patient. There were 39 abortions, of which 17 (44%) were spontaneous, 12 (31%) were elective, 6 (15%) were therapeutic, 3 (8%) were ectopic and one was unknown. In comparison, the majority of women participated in the national survey were white and younger, with a mean of 32 years of age. The mean number of children was 1.2 per woman. The mean number of elective abortions were similar between the two groups (0.14 vs 0.152) and the mean number of spontaneous abortions was lower in women with a history of IIM in comparison to the general population (0.198 vs 0.306) (Table 1).

Conclusion: Female patients with a history of IIM did not confer higher frequencies of poor pregnancy outcomes, including spontaneous or elective abortions. Rate of preterm pregnancies were similar, if not lower, to national averages. Differences between our patient demographics and birth rates in comparison to the national sample may be due to cultural and socioeconomic factors. Lastly, our cohort was limited by its inability to differentiate pregnancy prior to or during active IIM disease.

« Back to ACR Convergence 2023

ACR Meeting Abstracts - https://acrabstracts.org/abstract/pregnancy-outcomes-in-idiopathic-inflammatory-myopathies-a-comparison-to-the-general-american-population/