It is known that pregnant women who for various reasons have amniotic fluid loss, many hours or days before birth the fetus is exposed to an infection of both the fetus as the woman herself, known infection of Corio Endometritis Amniotitis or one that can even lead to peritonitis, much has been said then about the importance of these membranes, which prevent the amniotic fluid is lost, they represent a physical barrier against infection, but also in its composition as there are elements enzymes that prevent infection, becoming a biochemical barrier that defends the fetus from infection. In order to determine to what extent the presence of intact membranes in pregnant women is to complete a safety factor or guarantee the cleanliness of the amniotic fluid microbiological study was conducted on 60 samples of amniotic fluid in patients with term pregnancies , some free labor and other work in full delivery, all with intact membranes This work took place in the laboratory services of Obstetrics and Central Clinical Hospital of the North "Aguinaga Asenjo Mansur" of Essalud in Chiclayo Peru in the period between January and April 1990 all patients were cesarean section and samples were obtained in full surgical procedure by direct puncture of the membranes, two out of 60 samples were positive, isolated germs were Staphylococcus aureus in a sample (of the group who was in labor) and Enterobacter cloacae in another sample, the group that was not in labor. The results allow us to draw the following conclusions 1 .- The amniotic fluid in aseptic conditions was completely sterile in 58 cases and germs introduced into two of them which means a contamination in 3.3% of cases and is mostly sterile fluid. 2.-positive cultures of the two corresponded to a sample taken in the first period of labor, ie phase Latent Labor itself. 3.-No direct relationship was demonstrated sexual intercourse in the last month of pregnancy in the genesis of positive cultures of amniotic fluid, thus ruling out this reason Parea explain the presence of microbes in amniotic fluid. 4.-There is a possible direct link between the vaginal and genesis of positive cultures of fluid aniotico, because the two amniotic fluid samples were positive pregnant women were for the last month of pregnancy who underwent vaginal examination prior to surgery.