Objective: To examine the implantation potential of embryos from assisted reproductive technology cycles with low embryo production and to assess the effects of clinical variables and embryo scores (ES) on pregnancy outcome.
Design: Prospective clinical study.
Setting: Assisted reproductive technology unit in a tertiary medical center.
Patient(s): From July 1998 to December 2001, 280 cycles in 229 infertile couples produced a limited number of one, two, or three embryos 3 days after oocyte retrieval and underwent fresh embryo transfer (ET).
Intervention(s): Embryos with two or more blastomeres were scored and transferred.
Main outcome measure(s): ES and implantation rate per ET.
Result(s): Of 863 fresh ET cycles during the study period, 32.4% (280) were low embryo producers. Among them, there were no significant differences in average ES of individual embryos in single, dual, or triple ET or in embryos obtained from patients with low or high E2 responses, or young or old age. Embryos derived from conventional IVF had a better ES than those derived from intracytoplasmic sperm injection. The clinical pregnancy rate was strongly correlated with the cumulative ES. Implantation rates were similar among and between groups, with an average rate of 15.9%.
Conclusion(s): Embryos of low embryo producers had an inherently low implantation potential that appeared to be unrelated to the number of embryos transferred, female age, ovarian E2 genesis, or fertilization method. The cumulative ES can serve as a predictor of pregnancy.