PURPOSE: In the present study we evaluated, by light microscopy, and throughout morphometry, whether hypertrophy of cardiac striated muscular fibers of left ventricular occur in albino rat, during pregnancy. METHODS: After maiting, 12 nuliparous rats were divided into four groups with three animals for each group. The female rats corresponding to each group were killed at 1st, 7th, 14th and 21st days of pregnancy. RESULTS: Observation, on light microscopy (H.E) had at one view, did not display any alterations during pregnancy. However, the morphometry revealed that nuclei of cardiomyocytes are augmented in volume at 14th day of pregnancy and statistically significant data show the hypertrophy. CONCLUSION: The obtained data show the existence of a dinamic and reversible process of ventricular remodelling in consequence of adaptation physiological alterations of the cardiovascular normal pregnancy.