Purpose: to evaluate maternal hemodynamic and cardiac structural changes during the three trimesters of pregnancy and to relate them to the weight/gestational age of the newborn. Methods: twenty-two healthy pregnant women were submitted to echocardiography for the study of cardiac output, mean arterial pressure, left atrium diameter, and peripheral resistance during three periods of pregnancy, i.e., before the 12th week and at the 26thand 36th weeks of pregnancy. Seventeen pregnant women gave birth to infants with adequate weight for gestational age, four gave birth to small for gestational age newborns and one gave birth to a large for gestational age infant. Results: among mothers of low weight newborns, cardiac output and left atrium diameter remained constant, mean arterial pressure showed a tendency to increase and peripheral resistance was significantly increased (28%), during the gestation. Among the mothers of adequate weight newborns there was an increase in cardiac output of 19% in the second trimester and 8% in the third. The left atrial diameter increased approximately 9% during the gestation, with maintenance of mean arterial pressure and a tendency to a decrease in peripheral resistance. Conclusion: the present results support an association between hemodynamic adaptation and weight newborn.