548 Obstetrics and Gynecology Board Review •••
❍ What are normal semen parameters?
Traditional World Health Organization (WHO) reference values for normal semen analysis:
- Volume 1.5 to 5 mL.
- pH >7.2.
- Viscosity <3 on scale 0 to 4.
- Sperm concentration >20 million/mL (probability of conception rises then plateaus at concentrations
50 million/mL).
- Total sperm count >40 million/ejaculate (multiply semen volume by sperm concentration to determine count,
may be normal in oligospermia if volume is high or may be normal if the volume is low but the concentration
of sperm is high). - Percentage motility >50%.
- Forward progression >2 on scale of 0 to 4 (scale based on percentage of sperm moving forward, be it slow-grade
2, or rapid, grades 3-4, probability of conception increases up to 60% then plateaus). - Normal morphology (“Kruger strict criteria”) >14%, sperm morphology remains the best predictor of sperm
function. - Round cells <5 million/mL, epithelial cells, prostate cells, immature sperm, and leukocytes are all considered
“round cells.” - Sperm agglutination <2 on scale of 0 to 3.
❍ What was changed by the 2010 WHO revised reference value for lower limits of normal?
Lowered lower limit of normal sperm concentration to >15 million/mL.
Lowered percentage motility to >40%.
Lowered percentage normal morphology to >3 to 4%.
❍ What is the etiology of low volume acidic semen?
- Fact: Semen is made up of secretions from the seminal vesicles that are alkaline and contain fructose.
- Prostate secretions are acidic.
- Low volume could be due to incomplete collection or short abstinence interval.
- Congenital bilateral absence of the vas deferens (CBAVD) results in hypoplastic or absent seminal vesicles,
resulting in low-volume acidic ejaculate. - This is also found with ejaculatory duct obstruction; complete obstruction results in ejaculate with no fructose
or sperm. - When androgen levels are low, secretions from the seminal vesicles and the prostate are decreased.
- Postejaculatory urinalysis should be completed whenever the semen volume is <1cc to look for retrograde
ejaculation.
❍ What is azoospermia?
- Absence of sperm, affects 1% of all men and 10% to 15% of men with infertility.
- Obstructive versus nonobstructive azoospermia, 40% of the time obstructive.
- Must be confirmed on repeat semen analysis.
❍ What is oligospermia?
- Sperm concentration <20 million/mL, considered severe if <5 million/mL.
- Associated with varicocele, hypogonadism, and microdeletions in the Y chromosome.
- An endocrine and genetic evaluation is recommended in men with oligospermia.