Few organs or tissues are convenient to use for the pathologist to assess fetal maturity: the brain, particularly the external configuration of the cerebral hemispheres: the primary and secondary sulci appear in a definite chronologic order; the lungs; four developmental stages are defined: the last stage is characterized by attenuation of alveolar epithelial lining, and increase and superficial migration of capillaries. It must be reached necessarily to have postnatal respiration; the kidneys have a typical pattern of development, especially after 28 weeks, when it is possible to count the number of immature glomerular layers in the cortex; for the differentiation of the skin, specimens taken from special regions of the body are characteristic enough to determine the maturity, especially during the second trimester.