Xu, Kai‐Feng

Abstract Background: Lymphangioleiomyomatosis (LAM) is a rare, female-predominant, low-grade neoplasm that can lead to progressive diffuse cystic lung disease. Pregnancy has been associated with accelerated disease progression and increased risk of spontaneous pneumothoraces in women with LAM. Sirolimus is the current first line treatment for LAM and has demonstrated benefit in stabilizing lung function decline and reducing the risk of spontaneous pneumothoraces; however, there is unclear evidence regarding the risk benefit ratio of the use of sirolimus during pregnancy. Methods: We queried physicians across the LAM Clinic Network and obtained information regarding demographics, baseline characteristics, LAM related complications, lung function, sirolimus dosing, and pregnancy outcomes in women with LAM who took sirolimus during pregnancy. Results: We identified 9 women with LAM who had used sirolimus during pregnancy for a total of 12 pregnancies. All women had sporadic LAM with moderate lung function impairment prior to pregnancy: median FEV1 56% predicted, median DLCO 43% predicted, and 2 patients on supplemental oxygen. Sirolimus was used throughout pregnancy in most instances (10/12 (83.3%)). Sirolimus was held prior to pregnancy in 2 patients; both these patients experienced a spontaneous pneumothorax in the first trimester and resumed sirolimus in the second trimester with no further pneumothoraces during the rest of the pregnancy. The median sirolimus dose during pregnancy was 1 (range 1-2) mg daily with a median trough level of 2.95 (range: 1 – 6.7) ng/ml. Ten pregnancies (83.3%) resulted in live births, 1 pregnancy was terminated due to molar pregnancy, and 1 pregnancy resulted in miscarriage. Spirometry and DLCO were available in 8 pregnancies and tended to be stable (Figure 1). None of the 10 pregnancies that resulted in live births reported any fetal health issues. Seven out of these 10 children (70%) were breastfed with continued sirolimus use. At the time of submission of this report, the median age of these children is 3.5 years (range: 1 – 6.5 years) with no reported adverse health outcomes from sirolimus exposure during pregnancy. Conclusions: The use of sirolimus during pregnancy in women with LAM appears to be safe for both mother and fetus and might help reduce the pregnancy associated risks of accelerated lung function decline and spontaneous pneumothoraces.