Do low-quality embryos alter pregnancy rate in an assisted reproductive technology (art) program?

The number of embryos transferred in an ART cycle is a case-by-case judgment based on numerous factors including characteristics of the patient (age, medical history, etc.) and the quality of the embryos (cell stage, percent fragmentation, symmetry) available for transfer. A question of interest is whether the presence of a lower quality embryo together with high quality ones in a transferred cohort affects the likelihood of clinical pregnancy. To determine this, data concerning 337 ART cycles from 251 patients who underwent a transfer with at least two embryos were evaluated. The association of clinical pregnancy with several factors was investigated. The patients' ages were divided into the following groups: < 35 years of age, 35-37 years of age, and 38 and older years of age. Before transfer, embryos were inspected and the cell stages were determined based upon the total number of blastomeres per embryo. Furthermore, based on embryo shape, blastomeres symmetry, and percent fragmentation, a grade of one through five (1 = high quality vs. 5 = low quality) was assigned to each embryo transferred. Clinical pregnancy was defined as the presence of a fetal sac and a heart beat at 6-7 weeks post transfer. Using chi-square contingency tables, age has a significant effect on pregnancy rate (P = .032) as does the quality of embryos transferred (P = .002). However, age is not significantly related to the quality of the embryos at transfer (P = .44). Age is related to cell stage (P = .016), while cell stage is borderline related to clinical pregnancy (P = .059). Thus, age appears to affect clinical pregnancy rate through cell stage, but not through the quality score of the embryos being transferred. A logistic regression controlling for factors such as age and body mass index indicates that having at least one lower quality embryo transferred together with high quality embryos reduces the odds of clinical pregnancy.