Short Coincubation of Gametes in in Vitro Fertilization Improves Implantation and Pregnancy Rates: a Prospective, Randomized, Controlled Study

Objective: To examine the benefits of short coincubation of gametes compared to prolonged incubation in in vitro fertilization (IVF).

Design: Prospective randomized controlled study.

Setting: Hospital-based fertility center.

Patient(s): One hundred thirty patients (group 1) and 129 patients (group 2).

Intervention(s): Oocytes from group 1 were exposed to spermatozoa for 2 hours, and oocytes from group 2 were exposed to spermatozoa for 20 hours.

Main Outcome Measure(s): Fertilization and cleavage rates, embryo quality, and pregnancy and implantation rates were evaluated. Estradiol (E(2)) and progesterone (P(4)) levels were measured in the wells of culture dishes after 2-hour exposure of oocytes/zygotes to spermatozoa in group 1 and after 20-hour exposure in both the groups.

Result(s): There was no difference between the two groups in the fertilization rate and the number of embryos obtained. However, the proportion of grade 1 embryos was significantly higher among group 1 compared to group 2 patients. Clinical pregnancy and implantation rates were significantly higher among group 1 compared to group 2. The significantly higher levels of E(2) and P(4) in the 20-hour cultures compared with the 2-hour cultures may have been detrimental to embryo quality, pregnancy, and implantation rates.

Conclusion(s): Coincubation of gametes for 2 hours with standard or high insemination concentrations of spermatozoa significantly improved embryo quality and the pregnancy and implantation rates compared with overnight incubation of gametes.