Use of a medium buffered with N-hydroxyethylpiperazine-N-ethanesulfonate (HEPES) in intracytoplasmic sperm injection procedures is detrimental to the outcome of in vitro fertilization.

OBJECTIVE: This study was conducted to determine whether N-hydroxyethylpiperazine-N-ethanesulfonate (HEPES)-buffered medium used for the microinjection of sperm into oocytes may be detrimental for the embryo. DESIGN: Controlled randomized study. SETTING: Private IVF center. PATIENT(S): Women (n = 708) undergoing ICSI. INTERVENTION(S): The women were randomized into two study groups: 2,204 oocytes from 357 women were treated using a medium buffered with bicarbonate without HEPES during the ICSI procedure, and 2,168 oocytes from 351 women were treated using a medium buffered with HEPES during the ICSI procedure. MAIN OUTCOME MEASURE(S): Fertilization rate, degeneration rate, triploid rate, cleavage rate, embryo quality, pregnancy rate, implantation rate, and abortion rate. RESULT(S): Oocytes treated with a HEPES-buffered medium showed a statistically significant higher rate of triploid and degenerated oocytes after fertilization with ICSI compared with oocytes treated with a medium without HEPES. The embryos obtained from oocytes microinjected with a HEPES-buffered medium showed a statistically significant higher rate of highly fragmented embryos compared with the controls. Pregnancy rate and implantation rate were statistically significantly lower in the patient group with oocytes treated with the HEPES-buffered medium. The other parameters evaluated did not show any statistically significant differences. CONCLUSION(S): Our study showed that the use of media buffered with HEPES, during the microinjection of sperm into the oocytes, is detrimental for IVF outcome and should be avoided.

Number of embryos transferred and implantation.

Multiple pregnancies are considered the most frequent and serious complication of assisted reproduction technology. To reduce the frequency of multiple pregnancies, several centers have adopted a policy of reducing the number of embryos transferred in the uterus, suggesting single embryo transfer. Even though a significant number of papers have been published on this issue, no general consensus exists on how many embryos to replace in the uterus and at which cleavage stage. We conducted a retrospective study on cycles performed throughout 2003, analyzing the relation between the number of embryos transferred and the pregnancy and implantation rates, evaluating also the role of the woman's age. No differences were found among the groups except in one-embryo transferred women, which were mostly natural cycles, for estradiol levels, number of mature oocytes retrieved, number of top quality embryos, and pregnancy rate. The implantation rate was significantly higher in the two-embryo transfers versus three-embryo transfers. We found higher pregnancy and implantation rates with similar multiple pregnancy rates in patients where only two embryos were transferred versus three embryos transfer when women were less than 35 years old. In women aged less than 35 years, which in turn have the higher expectancy of successful pregnancy and also the higher risk of multiple pregnancy, the single embryo transfer is a suitable choice for these patients.