Sperm Count (TPMC) Impact on Time To Pregnancy

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Sperm count (TPMC) impact on time to pregnancy

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

doi.org/10.1093/humrep/deab133

Background

The findings of a study published in 2010 by the World Health Organization (WHO) is commonly used to interpret sperm (semen) analysis results.

In this study males who managed to get their woman pregnant within 12 months of ceasing contraceptives were grouped according to sperm results.

The sperm results of males in the bottom 5% of this study currently defines the minimum sperm count, concentration, motility, vitality, pH, volume and normal forms required for Doctors to classify a sperm (semen) sample as normal or abnormal.

However the use of this 5th percentile results to establish the minimum threshold values has been criticised due to the lack of correlation with fertility outcomes and should therefore not be used to differentiate between fertile and infertile men.

Total progressive motile sperm count (TPMC) was proposed in the 1970’s as a better means of assessing male factor infertility by combining semen volume, sperm concentration and progressive motility into one final number.

To date several studies have compared the predictive ability of TPMC against other individual sperm parameters and defined a TPMC > 20 million as ‘normal’ however there is a lack of large population-based data confirming the ideal TPMC for male fertility.

Aim

To define the individual sperm (semen) parameter ranges and thresholds best associated with time-to-conception in subfertile couples.

Methodology

To establish a sufficiently large study size data from the Subfertility Health and Assisted Reproduction and the Environment (SHARE) study was combined with the Utah Population Database (UPDB) covering a period between 1997 and 2017.

Males aged ≥ 18 years were automatically selected for the study however missing TPMC, pregnancy or birth data, azoospermic or sperm persevered samples and pre or post vasectomy samples were all excluded from final analysis.

Sperm analysis was performed according to the 4th (1999) or 5th (2010) edition of the WHO manual with all samples obtained after 2-7 days of abstinence.

Sperm morphology was not included in the final analysis due to changes in the WHO definitions, methodology in the laboratory and various data inconsistencies.

Thorough record keeping allowed various subgroups to be defined according to either natural, IUI or IVF assisted conception, with or without major female infertility diagnoses, including age > 40 years.

Total progressive motile sperm count (TPMC) was calculated as semen volume (mL) x sperm concentration (million/mL) x percentage of progressively motile sperm (eg 50% = 0.5).

Results

In total there was 6061 subfertile men analysed in this study of which 3957 (65%) had at least one live birth during the study period. Among this group of men the median time to pregnancy (conception) was 22 months. This includes men with IUI or IVF assisted conception and major female infertility cases.

Initial analysis showed that overall men with;

  • Sperm concentration ≥ 15 million/ml = 49% greater chance of a live birth
  • Progressive sperm motility ≥ 32% = 48% greater chance of a live birth
  • Total sperm count ≥ 39 million = 52% greater chance of a live birth

Within 5 years of the first sperm (semen) analysis, adjusted for male age.

Analysis of TPMC for this group found a TPMC of 1.2 million (bottom 5%), 110.9 million (median) and 462.0 million (top 5%) for men who fathered a child within 5 years.

A TPMC value of 50 million among this group of men was the best discriminate of men most likely to father a child within 5 years showing a 45% increase in chance and almost halving the time to pregnancy (19 vs. 36 median months).

Next, in the Natural Conception subgroup including major female infertility factor, 59.5% of couples achieved pregnancy without the use of IUI or ART in a median time of 27 months.

Analysis of these men showed that;

  • Sperm concentration ≥ 15 million/ml = 71% greater chance of a live birth
  • Progressive sperm motility ≥ 32% = 65% greater chance of a live birth
  • Total sperm count ≥ 39 million = 70% greater chance of a live birth

Within 5 years of the first sperm (semen) analysis, adjusted for male age.

In this group of men a TPMC ≥ 55 million showed a 55% increase in the chance of pregnancy within 5 years and more than halving the time to pregnancy (22 vs 58 median months) for these couples.

However Cox regression model graphs clearly show that only at TPMC ≥ 130 million does time-to-conception begin to plateau below 24 months for these couples.

Finally, in the Natural Conception subgroup without a major female infertility diagnosis, 62% of couples achieved pregnancy within a median time of 23.5 months.

Similarly analysis of these men showed that;

  • Sperm concentration ≥ 15 million/ml = 78% greater chance of a live birth
  • Progressive sperm motility ≥ 32% = 69% greater chance of a live birth
  • Total sperm count ≥ 39 million = 80% greater chance of a live birth

Within 5 years of the first sperm (semen) analysis, adjusted for male age.

In this group of men a TPMC ≥ 20 million showed a 80% increase in the chance of pregnancy within 5 years and a median time to pregnancy of 19.3 months.

Similarly Cox regression model graphs clearly show that only at TPMC ≥ 70 million does time-to-conception begin to plateau below 20 months for these couples.

Overall this study suggests that in a large group of men, with a ‘normal’ TPMC > 20 million, higher rates of pregnancy and a shorter time-to-conception may be possible by evaluating couples for contributing male factors and optimizing semen quality.

SUMMARY: HOW MANY SPERM NEEDED FOR PREGNANCY

The total number of progressively motile sperm (TPMC) needed to make a woman pregnant naturally is between 100 to 150 million, significantly increasing the rate of pregnancy and decreasing time to pregnancy compared to couples with a TPMC of only 20 million.

Limitations

  1. Retrospective study with all couples assumed to be trying to conceive after their first fertility evaluation for the entire study period.
  2. Database lacking detailed information on female fertility, sperm morphology and duration of infertility potentially underestimating time to conception and prevalence of female infertility.

Funding

No external funding was declared for this study.

Glossary

Median
The middle number of a sorted data set.

Percentile
The value below which a percentage of data falls.

Plateau
Little to no further change.

Semen
Organic fluid containing sperm.

Threshold
A defined value which may determine significance.

Similar studies

Hamilton J A, et al. (2015). Total motile sperm count: a better indicator for the severity of male factor infertility than the WHO sperm classification system. https://doi.org/10.1093/humrep/dev058

Slama R, et al. (2002). Time to pregnancy and semen parameters: a cross-sectional study among fertile couples from four European cities. https://doi.org/10.1093/humrep/17.2.503

Brasch J G, et al. (1994). The relationship between total motile sperm count and the success of intrauterine insemination. https://doi.org/10.1016/s0015-0282(16)56831-9

Small D R, et al. (1987). Interpretation of semen analysis among infertile couples. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1492115/


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