Objective As in many realms of academia and medicine, in obstetrics and gynecology, women experience gender bias in residency evaluations and academic promotions. More specifically, women in Maternal-Fetal Medicine (MFM) are underrepresented within departmental leadership positions. As a means of identifying spaces where bias may exist, multiple investigators have previously reported on gender bias in letters of recommendation (LORs) for residency and subspecialty training programs. We aimed to determine if linguistic differences exist in LORs for self-identified male and female applicants to MFM fellowship at an academic institution. Study Design This was a retrospective single-site cohort study from 2019 to 2021. Data collected included applicant's age, self-reported race/ethnicity and gender, geographic region of residency, step 1 and 2 scores, scholarly and volunteer activities, and number of LORs. The Linguistic Inquiry and Word Count (LIWC) software, a validated text analysis program, was used to characterize LOR linguistic content. Multivariable analysis was used to compare letter characteristics to applicant demographics. Results A total of 212 applications were reviewed, including 808 LORs. Women comprised 76.9% of applicants, and men 23.1%. Most applicants identified as non-Hispanic White (52.8%). Men were more likely to be international medical graduates (20 vs. 6%, p ≤ 0.01), and women reported more volunteer activities (7.1 ± 5.1 vs. 5.5 ± 4.3, p = 0.04). There were no differences in step scores, number of research projects, or number of LORs. Multivariable analysis controlling for applicant race, step 1 score, and gender of letter writer revealed that letters written for males contained significantly more references to the word category cognitive processes (7.4 ± 0.2 vs. 7.1 ± 0.1, p = 0.046), specifically in reference to the subcategories of certainty and differentiation. Conclusion We identified linguistic differences in LORs written for MFM applicants, suggesting potential bias in the style of writing for male and female physicians applying to this field. Key Points

INTRODUCTION: Multiple medical specialties have previously reported on gender bias in letters of recommendation (LORs). We aimed to determine if linguistic differences exist in LORs for male and female applicants to a maternal fetal medicine (MFM) fellowship at an academic institution. METHODS: This was an institutional review board (IRB)-approved retrospective single-site cohort study conducted from 2019-2021. Data collected included applicant’s age, race, self-reported gender, geographic region of residency, Step 1 and 2 scores, scholarly and volunteer activities, and number of LORs. The Linguistic Inquiry and Word Count (LIWC) software, a validated text analysis program, was used to characterize LORs’ linguistic content. Multivariable analysis was used to compare letter characteristics to applicant demographics. RESULTS: A total of 212 applications were reviewed, including 808 LORs. Women comprised 76.9% of applicants and men 23.1%. Most applicants identified as non-Hispanic White (52.8%). Men were more likely to be international medical graduates (20% vs. 6%, P=<.01), and women reported more volunteer activities (7.1 ± 5.1 vs. 5.5 ± 4.3, P=.04). There were no significant differences in Step scores, number of research projects, or number of LORs. Multivariable analysis controlling for applicant race, Step 1 score, and gender of the letter writer revealed that letters written for males contained significantly more references to the word category cognitive processes (7.4 ± 0.2 vs. 7.1 ± 0.1, P=.046), specifically in reference to the subcategories of certainty and differentiation. CONCLUSION: We identified linguistic differences in LORs written for MFM applicants, suggesting potential bias in the style of writing for male and female physicians applying to this field.