Objective
To evaluate the level of macrophage colony-stimulating factor (M-CSF) in serum in response to ovarian stimulation (group 1) in low-response (n = 26), moderate-response (n = 40), and high-response (n = 29) patients and to compare its changes (n = 23, group 2) throughout the menstrual cycle between pregnant and nonpregnant patients. Design: Randomized controlled trial. Setting: University IVF program. Patient(s): Ninety-five women undergoing IVF. Intervention(s): Serum and FF collection from 95 women. Main outcome measure(s): The M-CSF concentration was determined by ELISA. Result(s): The M-CSF levels in FF were higher than in serum. The M-CSF levels in serum increased from low-, through moderate-, to high-response patients; pregnancy rates were 11.5%, 22.5%, and 51.7%, respectively. Levels of M-CSF in serum increased throughout stimulation until the day of oocyte retrieval and decreased until ET. During the postretrieval days, from the day of ET, through implantation, to the day of confirmation of pregnancy, the M-CSF levels of those patients who became pregnant (n = 13) increased significantly and reached their highest level. After implantation the M-CSF level decreased slightly and reached a plateau during gestation.