Sample Collection & Handling
A clean semen sample is the foundation of every downstream result.
- 2–5 days: Abstinence window (WHO recommended range)
- ≤60 min: Analysis window (from collection to lab)
- ≥1.4 mL: Normal volume (WHO 6th edition)
- ≥7.2: Normal pH (alkaline ejaculate)
Why timing matters
Short abstinence lowers volume; long abstinence lowers motility.
Container & transport
Sterile, non-spermicidal cup kept near body temperature.
Liquefaction check
Coagulated semen must liquefy within 15–30 minutes.
Sperm Concentration Counting
A hemocytometer counts how many sperm pack into every milliliter.
- 16 M/mL: WHO lower reference (5th centile, 2021)
- ≥39 M: Total count reference (per full ejaculate)
- <16 M/mL: Oligozoospermia (low concentration)
- Neubauer: Counting chamber (improved grid)
Dilution & grid counting
Sample diluted, sperm counted across fixed grid squares.
Duplicate agreement
Two independent counts must closely match.
Clinical meaning
Low concentration alone does not guarantee infertility.
Progressive Motility Grading
Only sperm that swim forward purposefully can reach the egg.
- ≥30%: Progressive motility (WHO 5th centile)
- ≥42%: Total motility (progressive + non-progressive)
- <30%: Asthenozoospermia (low progressive motility)
- PR/NP/IM: Grading system (CASA classification)
Progressive vs non-progressive
Progressive sperm move mostly in a straight line.
CASA tracking
Computer software tracks flagellar beat and path.
Temperature sensitivity
Cold or delayed reading falsely lowers motility.
Strict Morphology Scoring
Sperm shape is graded head, neck, midpiece, and tail by Kruger criteria.
- ≥4%: Normal forms (WHO strict criteria)
- <4%: Teratozoospermia (abnormal morphology)
- Head shape: Common defect (round, tapered, pinhead)
- Papanicolaou: Staining method (standard smear stain)
Strict criteria origin
Kruger criteria compare sperm to cervical-mucus survivors.
Defect categories
Head, neck-midpiece, and tail defects scored separately.
Why the bar is low
Even fertile men rarely exceed 15% normal forms.
Sperm DNA Fragmentation Index
DFI measures broken DNA strands inside the sperm nucleus, invisible under routine analysis.
- <15%: DFI good prognosis (low fragmentation)
- 15–30%: DFI moderate (reduced natural fertility)
- >30%: DFI high (poor IVF/ICSI outcomes)
- SCSA / TUNEL: Common assay (flow cytometry based)
What causes fragmentation
Oxidative stress, heat, and varicocele damage sperm DNA.
Testing methods
SCSA, TUNEL, and Comet assays detect strand breaks.
Fertility impact
High DFI lowers pregnancy rates even with normal counts.