IntroductionChinese herbal medicine is widely used for treating polycystic ovary syndrome (PCOS). The present study aimed to explore the effects of Bu-Shen-Jian-Pi Formula, a Chinese herbal medicine formula, on the pregnancy outcomes of women with PCOS undergoing in vitro fertilization and embryo transfer (IVF-ET) based on a retrospective cohort study. MethodsOne hundred and forty-six females with PCOS undergoing IVF-ET were included in the study from Women's Hospital, School of Medicine, Zhejiang University between July 2016 and June 2021, of whom 73 patients received Bu-Shen-Jian-Pi Formula treatment for 12 weeks before IVF-ET, while the other 73 did not. The clinical data were collected from the medical records of the included patients. Bone morphogenetic protein 15 (BMP15) and leukemia inhibitory factor levels in the follicular fluids were detected. ResultsAfter the treatment of Bu-Shen-Jian-Pi Formula, women with PCOS undergoing IVF-ET exhibited significant improvement in the fertilization (P<0.05), good-quality embryo (P<0.01), clinical pregnancy (P<0.01), and live birth (P<0.01) rates, and single birthweight in newborns (P<0.05). The expression levels of BMP15 in the follicular fluids of the women with PCOS were significantly increased after Bu-Shen-Jian-Pi Formula treatment (P<0.05). ConclusionThis study provided preliminary evidence of a significant association of Bu-Shen-Jian-Pi Formula treatment with improved pregnancy outcomes in women with PCOS undergoing IVF-ET, partly through increasing BMP15 levels in the follicular fluids.