The Use of the Semen Analysis in Predicting Fertility Outcome
Authors: Arumugam Kulenthran , Omar Siti Zawiah 
Published: February 2008

This paper is a timely reminder of the poor relationship between semen analysis and fertility. On one hand low sperm motility and morphology did not reduce the pregnancy rates; on the other, the pregnancy rates were low despite normal semen, with over 50% not pregnant after 2 years.

Pregnancies with severely reduced semen quality

Although there were no pregnancies in the 5 couples with oligospermia in this study, it is important to remember that 5 % of MacLeod and Gold's 1,000 fertile men had sperm concentrations less than 20 million/ml. Conception despite severe oligospermia is documented in subfertile couples, during treatment of gonadotrophs deficiency, during male contraception and after vasectomy before sperm disappearance. While the F (fornication) factor may explain some of these pregnancies, paternity can not be disputed for all. The likelihood of pregnancy with sperm concentrations less than 5 million/ml is being examined prospectively in a trial of testosterone for male contraception.

Nature of infertility: distinction between sterility and subfertility

Some infertile couples have identifiable absolute barriers to reproduction ‐ azoospermia or obstruction of the Fallopian tubes, but many have either no abnormalities or, depending on the thoroughness of investigation and definition or normality, semen defects, or female pathology which may reduce fertility. The latter group produce pregnancies at a lower rate than normal (20–25%/month), but possibly as high as 5–10% per month without therapeutic intervention.

Statistical methods for investigating factors related to fertility

Floating numerator pregnancy rates (% pregnant) that ignore time are becoming infrequent in the literature and life table estimates are now common. Multiple regression (Cox) methods can be used to test the significance of groups of explanatory variables.

Semen variables and fertility

Semen variables related to pregnancy rates by Cox regression analysis of 448 pregnancies in 1,367 subfertile men were average sperm concentration and sperm autoimmunity; sperm motility and morphology were not significant (Baker et al, 1985). However both are important predictors of fertility in other studies.

Other prognostic factors: duration of infertility, female age

Additional pregnancy rate predictors include duration of infertility, previous fertility in the union and abnormalities in each partner. Female age is important: after the age of 35 years, conception rates fall from 85% to 50% in 1 year.

These prognostic factors are valuable for advising subfertile patients. However because the identified factors only explain a small proportion of the variance of pregnancy rates, the accuracy of prediction is limited.

New tests of sperm function: impact of IVF

IVF has facilitated studies of human sperm function. Sperm morphology is one of the most significant correlates of fertilization rate. The average linearity of sperm motility measured by video‐image analysis, percentage of sperm with intact acrosomes and the ability of sperm to bind to the zona pellucida are aslo related to the fertilization rate (Baker and Liu, 1989).

These new tests require assessment as predictors of fertility in vivo, but hopefully they will increase the accuracy of semen analysis.

Summary: The study investigates the use of the various parameters of the semen analysis in predicting the fertility outcome in 82 infertile couples. The sperm density, % progressive motility, % normal morphology were divided into ‘normal’ and ‘abnormal’ based on the criteria proposed by WHO. The subsequent cumulative pregnancy rates were then calculated according to this criteria. A life‐table method of analysis was used. All female related fertility factors were excluded. With the exception of a sperm density of < 20 times 106 per ml the other parameters showed no significant correlation with the cumulative pregnancy rates at 12 months or 24 months respectively. We concluded that the semen analysis does not predict the probable outcome of the subsequent rates even when female fertility related factors were excluded apart from a sperm density < 20 times 106 per ml.