Definitions are offered for the concepts of sterility and infertility. The notion of infertility is expanded to cover not only habitual abortions (three or more miscarriages) but, as well, deliveries of defective children. --Five-hundred and fifty-five pregnancies so far have occurred to 240 infertile probands, among them 78 with habitual abortions and 162 with damaged children. Only one in ten of those pregnancies resulted in clinically intact live birth. --Abortion was the result of 95 per cent of all pregnancies of the women with habitual abortion. The same applied to 25 per cent of all pregnancies of the above women with defective children (e.g. Down's syndrome, neural tube defects, diaphragmatic hernia, hydrocephalus, and progressive muscular dystrophy). A damaged child was born in more than 50 per cent of the latter pregnancy cases. --The number of children born by 162 women has been 181, with only 96 of them alive. The causality relationship between abortion and birth of defective children is discussed. --Infertile women should be given special attention, before conception takes place, and they should be kept under intensive care to the end of pregnancy.