Sperm morphology is a standard part of normal semen analysis testing. It indicates the percentage of sperm that have perfectly normal shapes as defined by specific criteria. Needless to say, few topics in male fertility provoke as much controversy and worry as sperm morphology. Patients and physicians alike are often extremely confused about the clinical significance of abnormally high levels of sperm shape abnormalities (called “teratospermia”).
Fortunately, a nice article was published earlier this year in the journal Andrology by Nicholas Gatimel and his colleagues from Toulouse, France. This article reviews the latest studies and recommendations regarding sperm morphology abnormalities. In today’s blog, I am going to provide you with an overview of some of the findings of this well-researched review.
Listed below are a few of the key points to keep in mind as you consider how your sperm morphology may be impacting your fertility potential:
#1) Variability- over the past few decades, meaningful interpretations of sperm morphology readings have been hampered by variations among labs in sperm slide preparations, the criteria used, and the subjective nature of evaluating the slides by lab technicians. Current recommendations are for patients to have semen evaluations at fertility-specific labs which use the latest 5th edition WHO criteria (in which a normal morphology is defined as ≥ 4% normal forms). Of note, the latest Kruger “Strict” criteria are essentially the same as the WHO 5th edition. However, the WHO 3rd edition criteria (normal ≥30%) is not very clinically useful in determining fertility potential.
#2) Elevated levels of sperm morphology defects are not associated with higher rates of sperm aneuploidy (i.e. sperm DNA defects) as compared to sperm with just low counts and motility. Elevated levels of sperm morphologic abnormalities should not significantly increase the risk of birth defects or health problems in subsequent children conceived using these sperm. A majority of studies have found that sperm DNA fragmentation is not felt to correlate with sperm morphology as well.
#3) Abnormal sperm morphology should not, by itself, be used as a reason to not attempt conception through natural intercourse if sperm counts and motility are otherwise decent. Higher sperm morphology levels are preferred, but persistent teratospermia should not, by itself, be an indication to immediately move on to more advanced treatments from the female side.
#4) Sperm morphology does not necessarily correlate with outcomes for intrauterine inseminations (IUI) in a majority of studies. Post-wash total motile sperm counts are the best predictor (from the male side) of IUI outcomes regardless of sperm morphology (though trying to improve sperm morphology as much as possible is recommended).
#5) Standard in-vitro fertilization (IVF) outcomes do appear to be correlated with sperm morphology (as defined by the 5th edition WHO guidelines). Consideration of using intracytoplamic sperm injection (ICSI) is recommended if the morphology is <4%.
#6) Intracytoplasmic Sperm Injection (ICSI) success rates do not appear to be correlated with sperm morphology in most studies, presumably because morphologically normal sperm can be individually selected for injection into each egg.
There are some rare exceptions to the recommendations above. Some of these exceptions include if none of the sperm have an acrosome cap (called “Total Globozoospermia Syndrome”), all of the sperm have large irregular heads (“Macrocephalic Sperm Syndrome”) or all of the sperm are headless (called “pin heads”). These and a few other very rare severe morphology defects can be associated with increased levels of sperm aneuploidy and DNA damage and have very low pregnancy success rates even with using IVF/ICSI.
For more detailed information on sperm morphology and its relationship to male fertility potential, please visit the “Morphology” section of the Male Infertility Guide at: