Objectives: To investigate whether a lower than expected number of oocyte after >= 14 mm follicle aspiration during OPU has any effect on pregnancy outcomes Methods: This is a retrospective study done between 2010 and 2013 at the IVF Unit of the Zeynep Kamil Women and Children Diseases Education and Research Hospital, dealing with the medical records of infertile patients who underwent IVF cycle and controlled ovarian stimulation with long agonist or fix antogonist protocol. The patients included into the study were those diagnosed with a primary infertility, aged between 23 and 39, at a BMI of 22-28 kg/m(2) and having received the first or second IVF treatment. Male factor, presence of uterine anomaly, patients with serious endometriosis and patients with low ovarian reserve were all excluded from the study. Typically, oocyte pick-up was performed in all the patients 35.5 hours after the hCG implementation. Single or double embryo transfer was performed, where available. Patients were classified into two groups. Group 1 consisted of those with no difference between >= 14 mm aspirated follicle number and expected number of oocyte or with 1 missing number of oocyte at the most. Group 2 consisted of those with at least >= 2 missing number of oocyte between aspirated follicle number and expected number of oocyte. Statistical analysis was performed using Student's t test for continuous variables and chi-square test for categorical variables. Additionally, a Linear regression analysis was conducted between the total number of oocyte and pregnancy. Results: In total, 387 treatment cycles were included into the study. Group 1 consisted of 134 patients and Group 2 consisted of 252 patients. Antral follicle number (12.8 +/- 4.3 and 14.5 +/- 4.1, P = 0.0007), hCG day E2 value (1990.7 +/- 1056.4 and 2515.2 +/- 1332.7, P < 0.0001) and the the number of aspirated follicle during OPU (9.1 +/- 4.4 and 13.7 +/- 5.5, P < 0.0001) were significantly higher in Group 2; whereas on the other hand, daily gonadotropin dose (290.9 +/- 79.9 and 273.4 +/- 74.4, P = 0.034) and total gonadotropin doses (2545 +/- 1031.8 and 2247.7 +/- 901.9, P = 0.004) were significantly higher in Group 1. The pregnancy rate was significantly higher in Group 1 (29.1% and 19.4%, P = 0.041). No correlation was observed between the number of oocyte and pregnancy (r = 0.082, P = 0.107). Conclusions: The number of aspirated follicles during IVF treatment being higher than the collected number of oocyte leads to a statistically significant fall in the pregnancy rates. There is no correlation between the number of oocyte and pregnancy.