ABSTRACT
OBJECTIVE: There are various factors affecting the outcome of human in vitro fertilization (IVF) programs. A retrospective study was performed to evaluate the influence of the factors on pregnancy rate of IVF programs. METHODS: From September 1994 to December 2001, 2604 IVF-ET cycles were performed from 1823 patients. The effects of ovarian response to controlled ovarian hyperstimulation, cause of infertility, age of patients, number of oocytes aspirated, number of embryos transferred, quality of embryos transferred, endometrial thickness, and type of IVF procedure on the pregnancy rates of the IVF-ET cycles were evaluated. RESULTS: Of 2604 IVF-ET cycles, 931 pregnancies (35.8%) were obtained from fresh embryos transfer (ET), and 78 pregnancies (20.1%) were obtained from 389 thawing ET cycles. Total 1009 clinical pregnancies were obtained, so the cumulative pregnancy rate is 38.7%. The pregnancy rates were significantly decreased in patients who were over 38 years old, showing poor ovarian response or having less than 8 mm of endometrial thickness (P<0.05). At least more than one Grade 1 or Grade 2 embryo transfer is requisite for maintaining over 40% of pregnancy rate. Limitation of embryos number for transfer to 3 is recommended for maintaining pregnancy rate and restraining multiple pregnancy rate. Transfer of zygotes or/and embryos into the oviduct is beneficial for improving the pregnancy rate, compared to transfer of embryos into the uterus. CONCLUSION: Pregnancy rate in IVF-ET is significantly affected by both endogenous and exogenous factors such as age, ovarian response, endometrial thickness, quality and number of embryos transferred, and method of IVF programs. Therefore, continuous effort to improve not only the controllable exogenous factors but the uncontrollable endogenous factors is necessary for increasing the pregnancy rate.