[Stereology of the myocardium in human fetus. Quantitative study of the structural changes in the last two trimesters of gestation]. / Estereologia do miocárdio em fetos humanos. Estudo quantitativo das modificações estruturais nos dois últimos trimestres de gestação.

PURPOSE: Quantitative study of the human myocardial comparing the 2nd and 3rd trimesters of gestation. METHODS: Fragments of the myocardium were collected from 8 fetal human hearts (4 from 2nd and 4 from 3rd trimesters) and prepared by histological methods. Fifteen random fields from each region were analyzed considering independently myocytes, connective tissue and vessels. Stereological determinations were possible by counting test-points and intersections on a multipurpose test lattice (M42). RESULTS: Stereological differences between last 2 trimesters of gestation were not significant (p > 0.05). The volume density was myocyte (including nucleus) = 75.6% in 2nd trimester and 67.7% in 3rd trimester; vessels = 3.7% in 2nd trimester and 6.4% in 3rd trimester; connective tissue (interstitial substance without vessels) = 20.6 to 25.9% for 2nd and 3rd trimesters respectively. However, considering the nuclei of the myocytes differences between last 2 trimesters were significant (p = 0.004). The volume density of the nuclei had a reduction from 2nd to 3rd trimesters (from 15.2 to 8.1% respectively). CONCLUSION: This result suggests decreasing synthesis of proteins from nucleus of myocyte in the last 2 gestational trimesters, but without quantitative important changes in the cardiac tissue, probably in relation to the reduction of the myocardial cellular multiplication.