Sperm morphology: classification drift over time and clinical implications

ObjectiveTo assess sperm morphology with Tygerberg (strict) and World Health Organization (WHO) 3rd criteria for intrauterine inseminations (IUI) between two eras to determine if there was a difference in pregnancy rates.DesignRetrospective study.SettingAcademic institution.Patient(s)127 couples with 290 IUI treatments during 1996–97 (era 1) and 133 couples with 317 IUI treatments during 2005–06 (era 2).Intervention(s)None.Main Outcome Measure(s)Pregnancy rates per cycle and couple.Result(s)Average sperm morphology was higher in era 1 than era 2 for both WHO 3rd (37 ± 13% vs. 23 ± 10%) and strict criteria (8.0 ± 5.0% vs. 4.0 ± 3.0%). Pregnancy rates per cycle were 5.9% versus 19.8% in era 1 and 16.7% versus 19.3% in era 2 for couples with WHO 3rd morphology <30% or ≥30%, respectively. Pregnancy rates per cycle were 2.7% versus 15.0% in era 1 and 13.3% versus 14.7% in era 2 for couples with strict morphology ≤4% or >4%, respectively.Conclusion(s)There was a strong relationship between morphology and IUI outcome in era 1 that was not present in era 2. These results suggest that classification drift increased the percentage of men diagnosed with teratozoospermia and resulted in a loss of predictive value.