Optic characteristics of breast tissues have been examined in mothers. An internation was designed to prevent and treat nipple fissures using individualized laser therapy regimens. Individualized laser therapy of 329 mothers at risk of mastitis and 68 mothers with a normal postpartum course reduced five-fold the incidence of mastitis in the risk group (from 18.6% to 3.7%, or to values characteristic of a normal puerperium). The wave length of 0.63 micron was found to be of a higher preventive and therapeutic efficacy, compared to the wave length of 0.89 micron. Laser rays activated the immune system, as reflected by rising serum levels of immunoglobulins A, M, G and lactoferrin. It is suggested that mothers with high trophoblastic beta-glycoprotein concentrations are at high risk of puerperal septic complications.