FIELD : medicine.SUBSTANCE : invention relates to medicine, namely to experimental medicine, cell biology. As a stimulator of fetal weight in a pregnant rat on the 9th or 10th or 11th day of pregnancy, subcutaneously inject 100?mcl of a suspension of human umbilical cord blood mononuclear cells containing 6.9?million cells into the area of each nipple of the breast. Total number of injected cells should be 69?million human umbilical cord blood cells in a volume of 1, 000?mcl.EFFECT : method allows to expand the arsenal of existing means to stimulate the fetal weight in the experiment and in clinical practice after obtaining permission for the clinical use of this method, and also to eliminate the use of anesthesia in a pregnant woman in the early stages of her pregnancy.1 cl, 1 tbl