Every man produces some ‘abnormal’ sperm, usually about half of all the sperm in each ejaculate. ‘Abnormal’ is therefore really a poor name for them because they are always there and are so common, although they probably do not fertilise an egg (hence they do not increase the chances of an abnormal baby). Each ejaculate is different so the proportion of ‘abnormal’ forms will vary considerably. Ejaculates from subfertile men usually have abnormal values for most the measurements – volume, motility, normal forms, concentration etc.