Sperm morphology is routinely evaluated as part of a standard semen analysis. Morphology refers to the size and shape of the sperm. The results of a sperm morphology exam indicate the percentage of sperm that appear normal when semen is viewed under a microscope. Abnormal sperm morphology may be a contributing factor in infertility.
Normal sperm have an oval head with a long tail. Abnormal sperm may have head or tail defects — such as a large or misshapen head or a crooked or double tail. These defects may impair the ability of the sperm to reach and fertilize an egg.
Causes of abnormal morphology include:
- Testicular abnormalities that are present at birth (congenital)
- Enlargement of veins within the scrotum (varicocele)
- High fever
- Illicit drug use
The best recommendation is to repeat the semen analysis in four to six weeks to determine if the changes in morphology are temporary or permanent. Even with poor morphology, pregnancy may still be possible. Intrauterine insemination or in vitro fertilization methods are sometimes needed.