Teratozoospermia is a condition where there are a large number of misshapen sperm found in a man's semen. Normal sperm morphology includes an oval-shaped head that is smooth, a well-defined cap, a connecting mid-piece, and a long straight tail.
Abnormally shaped sperm may have difficulties reaching an egg or passing through the outer layer of the egg, known as the zona pellucida. It is not uncommon for abnormally shaped sperm to contain an extra chromosome, be deficient a chromosome, or contain abnormal DNA.
Men with abnormally shaped sperm may have difficulty contributing to spontaneously conceived pregnancy.
FertilitySmarts explains Teratozoospermia
Male infertility is assessed through a semen analysis which is based on three factors: number of sperm (sperm count), motility (percentage of moving sperm) and morphology (percentage of abnormally shaped sperm).
There are two scales used to asses sperm morphology. Guidelines established by the World Health Organization (WHO) are considered to be more lenient as they do not classify as many sperm as abnormal. According to this scale, more than 96% of sperm need to be misshapen for a diagnosis of teratozoospermia. If a minimum of 5% of sperm appear to have normal sperm morphology, that is considered to fall within normal range.
The Krurger criteria is believed to be a more popular assessment model and provides a more strict analysis:
Mild teratozoospermia - between 14% to 10% of sperm have good morphology
Moderate teratozoospermia - between 9% and 5% of sperm have good morphology
Severe teratozoospermia - less than 5% of sperm have a good morphology
While the assessments do differ, both agree that issues related to sperm morphology require a high percentage of abnormal sperm: 96% for WHO and 85% in Kruger’s scale.
It is not uncommon for the cause of teratozoospermia to be unknown. Causes may include:
Exposure to toxins
Antiestrogens have been found to be a possible treatment for teratozoospermia. In addition, intracytoplasmic sperm injection (ICSI), where a sperm is injected directly into the egg can bypass issues caused by sperm shape or motility.