Semen parameter thresholds and time-to-conception in subfertile couples: how high is high enough?

Area of Science:

• Reproductive Medicine
• Andrology
• Human Reproduction

Background:

• Semen parameters are crucial for fertility evaluation, but individual values often don't definitively distinguish fertile from infertile men.
• Total progressive motile sperm count (TPMC) may offer a more comprehensive index for assessing male infertility severity compared to conventional parameters.
• Understanding thresholds for semen parameters can aid in counseling couples undergoing fertility evaluation.

Purpose of the Study:

• To determine thresholds for total sperm count, sperm concentration, progressive motility, and TPMC associated with earlier time-to-conception.
• To evaluate the predictive power of semen parameters for conception rates within 5 years.
• To inform patient counseling regarding fertility treatment.

Main Methods:

• A longitudinal cohort study included 6061 subfertile men from 2002-2017 with 5-year follow-up for conception data.
• TPMC was calculated as semen volume × sperm concentration × progressive motility percentage.
• Cox proportional hazard models and regression tree methods were used to identify thresholds and assess conception probabilities.

Main Results:

• A TPMC of 50 million was the optimal threshold for predicting earlier conception within 5 years in the overall cohort.
• Men with TPMC ≥50 million had a 45% greater chance of conception and achieved pregnancy earlier (median 19 months vs. 36 months).
• Higher semen parameters above WHO references consistently correlated with better conception rates and shorter time-to-conception.

Conclusions:

• A TPMC threshold of 50 million is a strong predictor of earlier conception in couples with male factor infertility.
• Optimizing semen parameters, even those within the lower normal range, can enhance conception chances.
• These findings provide valuable data for counseling patients on their fertility potential.