CHAPTER 3 Optional procedures 141
CASMA recordings. If the sperm concentration is low (<2 Ă&#x2014; 10 6 per ml), samples will need to be concentrated by centrifugation, as described in Section 2.13.2.2. Note: Centrifugation may affect sperm morphology and its use must be recorded.
Two studies have reported significant relationships between CASMA results and fertility endpoints. Coetzee et al. (1999c) found automated normal sperm morphology outcomes to be significant predictors of both fertilization rates in vitro and pregnancy. Garrett et al. (2003) found that the percentage of spermatozoa in semen that exhibited head morphology characteristic of those that are bound to the zona pellucida (â&#x20AC;&#x153;zona-preferredâ&#x20AC;?, %Z) together with straight-line velocity (VSL) in semen were significantly and independently related to natural pregnancy rates in a large group of subfertile couples. The relationships of both %Z and VSL with fertility appeared to be continuous, and no threshold value was identified above which there was no further increase in pregnancy rate. More studies of fertility outcomes in large populations are required to refine the application of CASA to measuring sperm morphology. Automated systems may have a role in providing data for quality control systems, but more research is needed to demonstrate their benefit for clinics.