Circulating levels of nitric oxide in successful and unsuccessful implantation after in vitro fertilization and embryo transfer. Relationship to estradiol and progesterone

Background. Nitric oxide (NO) may play an important role in embryo implanta tion and early embryo development. This study investigated the potential ro le of circulating nitric oxide (NO) measurement to predict the outcome of i mplantation and pregnancy after IVF and ET. Methods. Two blood samples were collected from 237 IVF patients on days 13- 14 and 20-21 after ET. Serum concentration of nitrite/nitrate (the two stab le oxidation products of NO metabolism), estradiol (E-2), progesterone and beta-hCG were measured on days 13-14 after ET and one week later. Results. No significant differences were found with respect to nitrite/nitr ate serum concentrations in conception versus non-conception cycles, viable versus abnormal pregnancies, and viable pregnancy group versus non-concept ion cycles, respectively, despite that significant differences were observe d regarding E-2 and progesterone values. Nitrite/nitrate serum concentratio ns were similar for singleton and multiple pregnancies at both study points . In viable pregnancies. no significant change was observed for nitrite/nit rate serum concentration from days 13-14 to 20-21 after ET. No correlation was found between N'trite/nitrate serum concentration and E-2 or progestero ne serum levels. Conclusions. Circulating levels of nitrite/nitrate are similar in successfu l and unsuccessful implantation after IVF and are unrelated to the outcome of pregnancy. This precludes the use of serum NO measurement as a marker of implantation and successful pregnancy in IVF.