Is Low Sperm Morphology Classified as Infertility?
Low sperm morphology alone does not classify a man as infertile—it is a weak predictor of fertility outcomes and should never be used in isolation to diagnose infertility or determine treatment pathways. 1, 2, 3
Understanding Sperm Morphology's Limited Diagnostic Value
The evidence strongly demonstrates that sperm morphology has poor discriminatory power between fertile and infertile men:
Multiple semen parameters assessed together predict fertility far better than any single parameter, including morphology. 1 The WHO strongly recommends evaluating concentration, motility, morphology, and volume in combination rather than relying on morphology alone. 4
Even when morphology shows the greatest discriminatory power among individual parameters, there is extensive overlap between fertile and infertile men across all ranges—making it non-diagnostic of infertility. 2
Recent meta-analyses demonstrate that sperm morphology is no longer predictive of pregnancy rates when using assisted reproductive technology (ART), and clinicians should not rely on percentage thresholds when deciding between treatment options. 5
Current WHO Reference Values and Their Limitations
The WHO lower reference limit for normal morphology is 4% (based on the 5th percentile of fertile men), down from the previous 15% threshold. 4, 6
This change has created controversy, as 67% of men with morphology between 5-14% were found to have identifiable contributing causes of male infertility (varicocele, hypogonadism, anti-sperm antibodies, etc.), suggesting the current threshold may miss clinically significant problems. 6
The subfertile range identified in landmark studies is <9% normal forms, with the fertile range being >12% normal forms, and values between representing indeterminate fertility. 2
Critical Assessment Requirements
At least two semen analyses separated by 2-3 months are mandatory before drawing any clinical conclusions due to significant intra-individual variability. 4 A single analysis is insufficient for diagnosis. 4
When evaluating low morphology, you must:
Calculate total motile sperm count (TMSC): concentration × volume × % motility. 4 TMSC >10 million per ejaculate is associated with good natural conception rates regardless of morphology. 4
Assess sperm concentration (lower reference limit: 16 million/mL) and motility (lower reference limit: 32% progressive motility) alongside morphology. 4, 2
Obtain hormonal evaluation (FSH, LH, testosterone) if concentration is <16 million/mL or if morphology is severely abnormal with other parameter abnormalities. 4
Clinical Decision Algorithm
For isolated low morphology with normal concentration and motility:
If TMSC >10 million and female partner has good prognosis (age <35, normal ovarian reserve), expectant management for 6-12 months is appropriate. 4
Morphology alone should not trigger immediate ART referral. 5
For low morphology combined with other abnormalities:
If concentration <5 million/mL with elevated FSH or testicular atrophy, obtain karyotype and Y-chromosome microdeletion testing. 4
If TMSC <10 million, proceed to intrauterine insemination (IUI) in natural cycles. 4
If multiple parameters are severely abnormal, IVF/ICSI offers superior pregnancy rates and eliminates morphology concerns through sperm processing techniques. 4, 7
Important Caveats
Sperm morphology assessment has major analytical reliability problems, with significant intra- and inter-laboratory variation in grading. 3, 8 The same sample assessed by different technicians or laboratories can yield vastly different results.
Except for specific rare defects affecting 99-100% of sperm (globozoospermia, macrocephaly, decapitated sperm syndrome), morphology assessment has very poor sensitivity and specificity for diagnosing infertility. 8
Never use morphology thresholds alone to counsel patients about fertility potential or to select between treatment modalities. 5 Base decisions on the complete clinical picture including female partner factors, TMSC, and duration of infertility.
Concentrations above 40 million/mL are associated with optimal fertility potential regardless of morphology percentage. 4