Right-sided ovulation favours pregnancy more than left-sided ovulation

The aim of this study was to evaluate whether frequency of ovulation and fe rtility potential of oocytes from the two ovaries differed in regularly men struating women (1057 cycles of 856 fertile women and 1033 cycles of 258 in fertile women). For both fertile and infertile women ovulation from the rig ht ovary occurred more often than from the left ovary (55 versus 45%; P < 0 .005), In infertile women follicular phase length was similar for right- an d left-sided ovulation, However, infertile women treated with intrauterine insemination (IUI) or in-vitro fertilization (IVF) showed a pregnancy rate in connection with right-sided ovulation (13%) which was higher than that o f left-sided (9%). The ratio of pregnancies deriving from the right ovary p er total number of pregnancies was similar in infertile and fertile women ( 64.6%, 73/113 and 63.4%, 361/569 respectively). The ratio of pregnancies fr om right-sided ovulation (similar to 64%) per total number of pregnancies w as higher than that of right-sided ovulation (similar to 55%) during non-pr egnant cycles (P < 0.0001). The implantation rate in right-sided ovulation seemed to be higher than in left-sided one, since IVF data showed a lower f requency (P = 0.03) of pre-embryo formation from right-sided ovulation than left-sided. Mid-luteal serum oestradiol and testosterone were higher (P < 0.05) in right-sided ovulation than left-sided. Taken together, in both fer tile and infertile women the fertility potential of oocytes from the right ovary surpasses that of the left ovary.