From the Guidelines
Normal Kruger criteria on semen analysis is defined as 4% or more of sperm with normal morphology. This strict criteria evaluates sperm head, midpiece, and tail shape, looking for oval heads with smooth contours, appropriate dimensions, and properly formed acrosomes. The midpiece should be slender and aligned with the head, while the tail should be straight and uncoiled. According to the American Urological Association and American Society for Reproductive Medicine recommendations 1, other parameters of semen analysis include:
- Ejaculate volume between 1.5 and 5.0 mL
- pH greater than 7.2
- Sperm concentration greater than 20 million per mL
- Total sperm number greater than 40 million per ejaculate
- Motility greater than 50 percent
- Forward progression more than 2 (on a scale of 0 to 4) Kruger morphology is important because sperm shape correlates with fertilization potential, with abnormally shaped sperm less likely to fertilize eggs. A result below 4% normal forms may indicate teratozoospermia, which could contribute to fertility issues. However, morphology is just one parameter of semen analysis, and should be interpreted alongside other factors like sperm count, motility, and volume. Men with low Kruger scores may still achieve pregnancy naturally or might benefit from assisted reproductive technologies like IVF with ICSI (intracytoplasmic sperm injection) if fertility issues persist.