Three pro-nuclei (3PN) incidence factors and clinical outcomes: A retrospective study from the fresh embryo transfer of in vitro fertilization with donor sperm (IVF-D)

Objectives: The aim of this study was to explore the main factors of 3PN incidence and determine whether the presence of 3PN could lead to a worse pregnancy outcome. Methods: This study included 508 IVF-D (in vitro fertilization with donor sperm) cycles from January 2013 to September 2014. The patients were divided into three groups as follows: group 1 included patients with no 3PN zygotes, group 2 included patients with 1%-25% 3PN zygotes and group 3 included patients with > 25% 3PN zygotes. Results: We observed that more retrieved oocytes and higher HCG day peak E2 value could result in 3PN incidence more easily. When the 3PN zygotes rate was > 25%, the percentages of normal fertilization (68.4% and 66.3% and 46.4%, P < 0.001), day 3 grade I+II embryos (41.2% and 38.6% and 25.8%, P < 0.001), day 3 grade I+II+III embryos (68.7% and 65.2% and 61.4%, P = 0.032) and implantation rates (52.1% and 50.8% and 45.4%, P = 0.026) were significantly lower than that in the other two groups respectively. The pregnancy rate was lower in 3PN > 25% group than that in the other two groups but there was no significant difference (65.2% and 66.7% and 55.6%, P = 0.266). The cleavage (98.3% and 97.2% and 98.2%, P = 0.063) and early abortion (7.1% and 8.0% and 8.6%, P = 0.930) rate were identical among three groups. Conclusions: More retrieved oocytes and higher HCG day peak E2 value could result in 3PN incidence more easily. Interestingly, normal fertilization rate, day-3 grade I+II embryos rate, day-3 grade I+II+III embryos rate and implantation rate were significantly lower in IVF-D cycles with a 3PN incidence of > 25%. The number of day-3 grade I+II embryos might be a key factor for pregnancy in IVF-D cycles with a 3PN incidence of > 25%.