What is Sperm Morphology?
Morphology is assessed under a microscope using strict (Kruger) criteria. A normal sperm has an oval head, an intact midpiece and a single straight tail. Under WHO 2010 criteria, a normal sample has at least 4% normally shaped sperm — yes, only 4%. Lower than this is called teratozoospermia, but it does not mean infertility on its own.
What Causes Abnormal Morphology?
Genetic factors — some abnormalities are inherited
Heat exposure damaging developing sperm
Varicocele — a leading reversible cause
Infections of the reproductive tract
Smoking, alcohol and recreational drug use
Exposure to toxins, pesticides or radiation
Hormonal imbalances during sperm production
Advanced age
What Does it Mean for Conception?
Many men with low morphology conceive naturally — it is only one factor
Combined with low count or motility, the impact is greater
Lifestyle changes can improve morphology over 2-3 months
IUI is sometimes used for mild cases
IVF with ICSI is highly effective: an embryologist selects the best-shaped sperm and injects it directly into an egg, bypassing morphology issues
When to Take Action
Always interpret morphology alongside count and motility — not in isolation
Repeat the test after 8-12 weeks before drawing conclusions
Lifestyle and antioxidant interventions can help
See a fertility specialist if morphology is consistently low and you are struggling to conceive