BACKGROUND: A significant proportion of women in reproductive age are diagnosed with diffuse gliomas, resulting in the need to address the safety of pregnancy in patient consultation. However, data on glioma progression after and during pregnancy are sparse and controversial. METHODS: Female adult patients in their reproductive years (≥18 years and <
46 years) with histological diagnosis of glioma between 01/01/2000 and 01/12/2019 from 2 academic centers have been included in the study. Re-classification according to the 2021 WHO classification of CNS tumours was performed. The cohort was divided into 3 groups, defined as (A) nulliparae, (B) primi-/multiparae before glioma diagnosis, and (C) primi-/multiparae after glioma diagnosis. Survival analyses were performed in a time-dependent manner with parity as time-dependent covariate. RESULTS: 159/368 females met our inclusion criteria, resulting in 47 (29.6 %) nulliparae, 88 (55.3 %) primi-/multiparae before glioma diagnosis and 24 (15.1 %) primi-/multiparae after glioma diagnosis. Median follow-up was 127.4 months (range 0.7-341.9), and median overall survival and progression free survival were 247.6 months (range 0.4-269.1) and 67.9 months (range 0.7-341.9), respectively. Overall, 113/159 (71.1 %) patients had tumour progression and 53/159 (33.3 %) deceased. In total, 57.4 % of the nullipara, 76.1 % of the primi-/multipara before glioma diagnosis and 79.1 % of the primi-/multipara after glioma diagnosis groups experienced tumour progression (p >
0.05). In multivariate time-dependent analysis, primi-/multiparae after glioma diagnosis presented with shorter progression free (HR 2.45, p = 0.0079), but not overall survival (HR 0.54, p >
0.05) in comparison to the other two groups. CONCLUSION: Pregnancy after glioma diagnosis was associated with shorter progression free survival. Longer follow-up as well as larger cohorts are needed to investigate a potential impact on overall survival.