Incubator temperature is one of the most precious variables in IVF labs. When the IVF started, almost all incubator temperatures were set at 37 degrees which mimic in vivo conditions. Some authors speculated that gametes and early embryos might need low temperatures that provide quieter metabolism. We decide to compare Embryo culture at 37 degree or slightly lower 36.5 degree and extensively investigate to find which is better to crucially introduce a solid evidence through this RCT.

Since the first IVF birth in 1978, the field of assisted reproductive technology has evolved dramatically. The evolution includes both the ovarian stimulation protocols and the laboratory techniques. Optimization of the laboratory procedures is of great interest to the scientists in the field of IVF.

Incubator temperature is one of the most precious variables in IVF labs. When the IVF started, almost all incubator temperatures were set at 37 degrees which mimic in vivo conditions.

Some authors speculated that gametes and early embryos might need low temperatures that provide quieter metabolism. another group found increase in pregnancy rate for embryos cultured below 37 degree compared to those cultured at 37 degree. Nevertheless; the majority of embryologists still consider culture at 37 degrees is the back bone for the incubators.

The paucity of well designed studies makes it difficult to achieve a satisfactory answer whether lower temperature will improve the pregnancy rate. This encourage us to study the effect of lower temperature (36.5 degrees) on the pregnancy rate compared to conventional temperature (37 degrees).

Inclusion Criteria:

• Women aged ≤ 33 years
• BMI ≤ 33
• Normal responder ( ≥ 8 MII )
• Fresh cycle
• First attempt (or with previous successful attempt)
• Normal or mild oligoasthenoteratozoospermia

Exclusion Criteria:

• Testicular sperm
• < 8 MIII collected
• Difficult transfer cycle
• endometriotic patients
• Poor Endometrium < 8mm diameter at OPU