New method to estimate the possibility of natural pregnancy using computer-assisted sperm analysis.

The World Health Organization (WHO) criteria, which include percent motility and sperm concentration, are the only criteria for evaluating sperm quality and conception ability. However, these criteria are insufficient to evaluate the possibility of natural pregnancy. Thus, an index that can directly evaluate the possibility of a natural pregnancy is necessary. A new sperm energy theory without approximation was developed to assess the possibility of natural pregnancy based on mechanical sperm energy. Sperm motility parameters were measured using computer-assisted sperm analysis (CASA) in 129 ejaculated semen samples from 50 men in couples diagnosed with infertility, in which no abnormalities were found in women (sterile group), and 157 ejaculated semen samples from 57 men who had already fathered children in natural pregnancies (control group). A total of 129 subjects were selected from the control group and classified as the fertile group in order of the sample measurement date. The sperm energy index (SEI) and mean sperm energy index (MEI) were accurately obtained according to the methods described by the new sperm energy theory. SEI reflects total mechanical energy of the sperm in a visual field during CASA measurements. MEI reflects the mean mechanical energy of one sperm in a measurement field. All subjects with (MEI)/(SEI) > 2 were assigned to the sterile group. The larger the SEI, the higher was the probability of predicting fertile subjects. The probability of predicting fertile subjects was approximately 60% with a SEI of > 0.5, 70% with a SEI of > 1, 80% with a SEI of > 3, and 90% with a SEI of > 6 in cases where (MEI)/(SEI) is < 2. The data support the view that this novel method can be used to estimate the possibility of a natural pregnancy.