The success of IVF is influenced by factors as cause of infertility and age. Furthermore, there is a large influence of external factors, from the laboratory environment, handling and cultivation of gametes and embryos. The existence of factors capable of affecting the success of the treatment lead to the need of a quality control to attenuate the unfavorable effects.

After ovarian stimulation, follicular aspiration is performed. At this moment, factors such as aspiration technique, needle type and temperature are the main variables to be controlled. It is known that oocytes are the more sensitive cells to temperature fluctuations. Currently, the standard protocol for follicular aspiration does not include the warming of the aspiration needle. However, due to the existing evidence in the literature, that the follicular fluid temperature drops during the aspiration procedure, this work aims to evaluate the influence of a pre warming of the aspiration needle as a new protocol.

The estimated sample was 600 oocytes for each group, totaling a minimum of 1200 oocytes, considering a fertilization rate of 65% in the control group and 73% in the study group, for a power of 80% and p alpha 5%, i.e. , an increase of more than 10% between groups. As there is no data in the literature, when the investigators have this sample an interim analysis to evaluate the data will be performed. The investigators consider 10% a reasonable difference that can (with this sample size) increase by 48 embryos and a possible increase of 7 pregnancies within this sample. Bearing in mind that the average number of oocytes retrieved per patient is 6 oocytes, the investigators estimate that 200 patients will be needed to reach the calculated sample number.

The warm-up protocol will be applied by the embryologists, which consists of heating the follicular aspiration needle to 37 Celsius, overnight, the day before the day of the ovarian aspiration procedure.

The variables that will be compared between the studied groups are the rates of oocyte retrieval, maturity (MII), fracture, atresia, fertilization rates and discarded embryos.

Continuous variables will be analyzed using Student's t test if they have normal distribution, for comparison of means between two independent groups or the Wilcoxon-Mann-Whitney U test if not parametric. Differences between groups will be considered significant when p<0.05.

Inclusion Criteria:

• All women submitted to IVF cycles

Exclusion Criteria:

• Women submitted to follicular aspiration due to oocyte cryopreservation
• Patients without oocyte retrieved
• Patients without mature oocyte retrieved
• Procedures with needle replacement