Received March 02, 2013
Accepted March 13, 2013

Objective: To determine the chance of pregnancy and the risk of multiple pregnancies taking into account the number and quality of transferred embryos in patients > 36 y-old or ≥ 36 y-old. Methods: This case control study included 1497 patients undergoing intracytoplasmic sperm injection (ICSI) cycles. Cycles were split into groups according to the number and quality of the transferred embryos on the third or fifth day of development. The pregnancy rate and multiple pregnancy rate were compared between the embryo quality groups in patients <36y-old or ≥36y-old. Results: In patients <36y-old, for the day three embryo transfer, no significant difference was noted in the pregnancy rate when the groups were compared; however, the multiple pregnancy rate was increased by the transfer of an extra low-quality embryo (17.1% vs 28.2%, p=0.020). For day five embryo transfer, the transfer of an extra blastocyst significantly increased the pregnancy rate (36.0% vs 42.4%, p<0.001) and the multiple pregnancy rate (4.4% vs 16.9%, p<0.001). In older patients, no significant difference was noted in the pregnancy rate when the groups were compared; however, when an extra low-quality embryo was transferred, a significantly increased rate of multiple pregnancies was observed for day three (18.2% vs 26.4%, p=0.049) and day five embryo transfers (5.2% vs 16.1%, p<0.001). Conclusions: The transfer of an extra low-quality embryo may increase the risk of a multiple pregnancy. In younger patients, the transfer of an extra low-quality blastocyst may also increase the chance of pregnancy.