Sperm morphology can't predict intrauterine insemination pregnancy rate

April 1, 2008

Mounting evidence suggests that the appearance of sperm has little to do with its function.

Intrauterine insemination is less invasive and less expensive than other forms of assisted reproductive technology; thus, it is often used as first-line treatment for couples with male factor or unexplained infertility. Many couples in which the man has poor sperm morphology are often directed to undergo more extensive fertility treatments on the assumption that IUI would not achieve successful impregnation. This may be poor advice, according to Phoebe M. Hughes, MD, a resident in obstetrics and gynecology at the Mayo Clinic, Rochester, MN.

Investigators found no differences in pregnancy outcomes for the three Strict categories (<4%, 4-9%, >9%) and the two WHO morphology categories (<30% and ≥30%).

"We had a large proportion of abnormal sperm, with nearly half of the patients falling in the poor prognosis (<4%) group," Dr. Hughes noted.

In spite of statistically significant differences in total motile sperm/insemination by both the Strict and WHO categories and significant differences in percentage of motile sperm by the WHO categories, little difference in pregnancy outcome was observed.

"These data suggest that sperm morphology, as assessed by either criterion, does not affect IUI clinical pregnancy rate," Dr. Hughes said. "One reason morphology may not be predictive of IUI outcome is the fact that Strict morphology analysis has become too strict over time. Others have demonstrated this, and it leads to overdiagnosis. Thus, the predictive value of morphology is lost as the number of patients with an abnormal morphology reading increases.

"Meanwhile, our conclusion is that IUI is a simple and cost-effective method of assisted reproductive technology. The recommendation of whether or not to attempt this [procedure] based on sperm morphology assumes that the probability of achieving a successful pregnancy would be small using sperm with poor morphology. These data, however, reveal that acceptable pregnancy rates can be achieved even with poor morphology."