To study the effect of exosomes in the follicular microenvironment on the in vitro fertilization (IVF) pregnancy outcome, and to clarify the source of exosomes in the follicular microenvironment.

A total of 200 young patients with normal ovarian function who underwent IVF therapy were recruited in this retrospective study. The patients were divided into two groups (pregnancy and non-pregnancy) according to the pregnancy outcome.The morphology of exosomes in follicular fluid was observed and the concentration of exosomes was detected. The logistic regression analysis and multivariate partial correlation were used to analyze the factors affecting oocyte quality and pregnancy outcome. The source of exosomes was identified by polymerase chain reaction （PCR）.

The baseline follicle stimulating hormone (FSH) level (r=0.17, P=0.017) and the concentration of exosomes in follicular fluid (r=0.881, P<0.001) were independent factors affecting the rate of high-quality embryos. Antral follicle count (AFC) (B=0.107, P=0.033) and the concentration of exosomes in follicular fluid (B=0.419, P<0.001) were independent factors affecting the pregnancy outcome. The results of PCR showed that exosomes of both groups expressed growth differentiation factor (GDF) 9 and bone morphogenetic protein (BMP) 15 gene transcripts of oocyte markers.

The concentration of exosomes in follicular fluid was an independent factor affecting the rate of pregnancy outcome. The exosomes in the late development follicular fluid are derived from oocytes

Exosome; Follicular microenvironment; Follicular fluid; Pregnancy outcome; Fertilization in vitro; Embryo transfer