Ovulation pattern affects pregnancy rate and sex of offspring

Ovulation pattern affects the likelihood of achieving pregnancy and the gender of offspring produced from the eggs, Japanese researchers report.

Their study investigated whether the pattern of ovulation in 3 consecutive menstrual cycles influenced the pregnancy rate and sex of offspring in 335 women undergoing in vitro fertilization or intrauterine insemination. A pattern of left-left-right ovulation produced the highest pregnancy rate (27%) and live birth rate (22%) compared to all other possible patterns. This pattern also resulted in a significantly higher ratio of male-to-female offspring (0.762).

Lead author Misao Fukuda, MD, speculates that “the oocyte following an LLR ovulation pattern, freed from the suboptimal effects from the dominant follicle and/or the corpus luteum during 2 previous menstrual cycles, is well matured and prone to be receptive to Y sperm.” Y-sperm, which are smaller than X sperm “could easily penetrate the zona pellucida of the oocyte following LLR,” he says.

“It appears that when human reproduction is under pressure or unfavorable conditions, more females tend to be born. Y sperm or XY embryo might be more fragile, vulnerable, and sensitive than X sperm or XX embryo.”

“Large-scale observational studies are necessary to confirm that the present finding is correct,” Fukuda cautions. “Next, comparison of health status of preantral follicles and/or early stage of antral follicles from between the ovaries with and without dominant follicle or corpus luteum would be of interest.”

The study was published online March 5 in Fertility and Sterility.