Received September 28, 2015
Accepted December 30, 2015

Objective: To assess the correlation between low levels of progesterone and ovulation by ultrasound monitoring in infertile patients with regular menstrual cycles. Methods: Case-control study. The sample consisted of 302 women aged 20-40 years, treated from 2000 to 2014 in the Human Reproduction Laboratory of the University Hospital of the Federal University of Goiás and in the Department of Gynecology and Obstetrics in Goiânia, Goiás. Data collection was performed by analysis of physical records (Medical Records and Health Information Services) and electronic ones (Sisfert©, 2004) after approval by a Human Research Ethics Committee. Patients were classified according to their ovulatory status, evaluated by progesterone levels and ultrasound monitoring and divided into two groups: Group I (anovulatory cycle patients, n=74) and Group II (ovulatory patients, n=228). In both groups associations were made between the percentage of patients with normal progesterone (≥ 10 ng/ml) and percentage of patients with low progesterone (5.65 - 9.9 ng/ml). The groups were paired for comparisons related to age, body mass index, duration of infertility, follicle stimulating hormone (FSH), thyroid stimulating hormone (TSH), luteinizing hormone (LH) and estradiol (E2). Results: There was a significant association between the percentage of ovulation by ultrasound monitoring and the percentages of patients who presented low levels of progesterone. Conclusions: The study suggests that low serum levels of progesterone are associated with low percentage of ovulation in infertile women with regular menstrual cycles and women with unexplained infertility.