Presence of endometrial fluid (EF) is a poorly understood pathology and remains a challenge for clinicians, as very little data exists to explain its consequences and treatment. Our objective was to investigate risk factors for EF during IVF.

This retrospective cohort study included all women with a freeze all embryos cycle (FAE) for EF between 2010 and 2016 at a university-affiliated private IVF center. Controls (2:1) were randomly selected out of the database of our fresh autologous IVF cycles during the same period. Main outcome measures were possible risk factors for EF, comprising polycystic ovarian syndrome (PCOS), ovarian hyperstimulation syndrome (OHSS), previous pelvic or endometrial surgery (polypectomy or synechia removal), cesarean section, myomas and severe endometriosis. A logistic regression model was used to assess independent risk factors for EF.

Out of 9000 IVF cycles, 1204 were FAE cycles, among which we identified 86 EF cases. We then selected 171 controls. Independent risk factors for presence of EF were a history of previous myomectomy (adjusted odds ratio (aOR) 19.77, 95%CI [4.01-97.53]), severe endometriosis (aOR 5.97, 95%CI [2.09-17.05]), PCOS (aOR 5.72, 95%CI [2.66-12.33]) and previous cesarean section (aOR 5.17, 95%CI [1.84-14.49]).

Our results are not only confirming the association between PCOS, severe endometriosis, previous cesarean procedure and EF, but also reporting for the first time an association between previous myomectomy and EF.