The prevention of infection in pregnancy is critical to provide an appropriate fetal development and term delivery. Natural antimicrobials are the mediators of innate immune system with antibacterial, anti-viral and anti-fungal properties. It has been found that these antimicrobials play the great role in a homeostasis of bronchial and intestine epithelium, endometrium and epidermis. The activity of elafin--neutrophil elastase inhibitor--has been found in female reproductive system microenvironment (cervix, endometrium and fallopian tube) with the highest expression in the endometrium of non-pregnant women during ovulation and menstruation. The influence of elafin has been established on the maintenance of early pregnancy and the patomechanism of preterm labor and other pathology of pregnancy. Elafin level in amniotic fluid has been confirmed to be decreased in cases of preterm rupture of membranes (PROM). The protein may be a good marker of preterm labor and use in its diagnostics and treatment.