Sperm morphology as diagnosed by strict criteria: Probing the impact of teratozoospermia on fertilization rate and pregnancy outcome in a large in vitro fertilization population

Objective: To investigate the predictive value of sperm morphology assessed by strict criteria on IVF outcome. Design: Retrospective analysis of all IVF cycles (January 1987 to December 1992). Main Outcome Measures: All patients were assigned to one of three groups based on sperm morphology: P- pattern (<4% normal forms), G-pattern (4% to 14% normal forms), and N- pattern (>14% normal forms). Morphology pattern was related to other semen characteristics and IVF outcome. Results: Despite corrective measures at oocyte insemination, the fertilization rate was significantly different among the three morphology groups, P < G < N. N-pattern sperm produced a mean fertilization rate over 85% regardless of low motility or concentration. In a cohort study, P-pattern cycles produced a lower implantation rate and lower ongoing pregnancy rate, independent of the lower fertilization rate. Conclusions: Strict morphology is an excellent biomarker of sperm fertilizing capacity, independent of motility and concentration. P-pattern sperm may denote a poorer prognosis for establishing a pregnancy, even after a satisfactory fertilization rate is achieved.