Background & objectives : Infertility is a global problem affecting millions of men and women in developed and developing countries. In this regard, in-vitro fertilization (IVF) plays an important role in improving the quality of life in infertile patients. However, studies have shown that the implantation failure in IVF is the main challenge of this procedure. Melatonin can increase the survival rate of embryos and IVF success rate through eliminating free radicals and removing reactive oxygen species. So, this study is conducted to investigate the effects of different concentrations of melatonin on the rate of newborns of mice following transfer oftwo-cell embryos .

  Methods : In this study, female mice with average age of six to eight weeks were superovulated by administering pregnant mares serum gonadotropin (PMSG) intraperitoneally (7.5 IU. ip), and followed after 48h by human chorionic gonadotropin (hCG) (7.5 IU. ip). Two-cell mouse embryos were obtained from female mice oviduct after 48 h. The embryos transferred bilaterally into pseudopregnant mice of the same strain through surgical procedure and 8-14 embryos were transferred to each tube. The study included 4 treatment groups and one control group (6 mice in each group). The treatment groups were exposed to subcutaneous injection of concentrations of 100 µm , 10 µm , 1 µm and 100 nm of melatonin. After the cesarean on 18^th day of pregnancy, the percentage of live births was assessed. The outcomes of the live birth rate were as­sessed using the chi-square test and statistical analyses were carried out using SPSS version 16.0. Percentage of live birth was calculated and compared with the control group.

  Results: A total of 701 two-cell mouse embryos were transferred into one control group and four experimental groups. The number and percentage of live births at concentrations of 100 µm and 10 µm of melatonin and the control groups were 21 (15.55%), 13 (9.15%) and 9 (6.47%), respectively. No infant was born at the concentrations of 1 µM and 100 nM of melatonin . The highest rate of live births was obtained at the concentration of 100 µM and showed a significant difference with the control group (p ≤ 0.01). There was no significant difference in live births at the concentration of 10 µm and control group.

  Conclusion : The results of this study indicated that subcutaneous injection of melatonin improves the two-cell mouse embryo growth and post implantation development of mice.