Intestinal microbiota is a crucial element enabling the maintainance of proper health of a person from the moment of birth. It protects from pathogenic bacteria colonization as well as regulates important metabolic functions of the organism. The development of the intestinal microflora from birth, is an essential factor determining proper functioning of the organism throughout the whole life. The normal colonization with microorganism of the intestinal tract is crucial for maintaining homeostasis of the whole body, and its changes may lead to permanent effects influencing the functioning in the future life. The biggest impact on the colonization has the type of birth and the methods of feeding in the first hours of life. Delivery by cesarean section disrupts the physiological bacterial colonization of the digestive tract. Cesarean section is the most frequent procedure performed in female patients worldwide. According to WHO recommendations, this procedure should not exceed more than 5 to 15% of all the deliveries. However, the polish and international data shows that the percentage of births via cesarean section is much higher [1]. In the year 2011, 300 cesarean sections were performed per 1000 births in Poland [2]. Experience and observations from many neonatal clinics confirm that the digestive tract is mostly sterile and the colonization with bacteria occurs in the moment of birth. However current data shows that the intrauterine environment is not sterile and there are many factors, during the fetal life which influence the fetal organism as well as the composition of the microbiota. Authors [3] present that some microorganisms can be found in the meconium of some preterm infants. Moreover it was also proven that amniotic fluid from the mothers of premature deliveries contains a big spectrum of bacteria rDNA [4]. Another very important factor influencing the colonization of neonatal digestive duct, is the method and time of feeding. The best food for the infant is the breast milk of the mother and colostrum plays a unique role. Breatfeeding with it in the first days of the infant, helps colonization of the intestines with physiological flora and development of proper immunological response. A delay in the initiation of breast-feeding after cesarean section, has a negative influence on the development of the microflora in infants with the favor for potentially pathogenic bacterial species. Colonization occurs in the first week of the infant’s life. The upper part of the tract is colonized with bacteria which are normally found in the oral cavity, the lower part of the tract is occupied by microflora characteristic for the lower part of the digestive tract of the mother. The method rooming-in favors colonization of the digestive tract by physiological species and initiation as well as continuation of breast-feeding [5]. Intestinal dysbiosis can be the basis for many diseases [6]. Therefore the knowledge of prenatal and postnatal factors influencing the bacterial colonization of digestive tract in infants is important. The process of bacterial inhabiting the digestive tract has its importance in the long-term aspect of evaluation of organism defense.

Key words: colonization, cesarean section, neonatal, breast-feeding.