To assess and compare the ejection fraction (EF) and shortening fraction (SF) of both ventricles through pregnancy. Uncomplicated singleton pregnancies, of between 10 and 40 weeks' gestation, were recruited. Transabdominal two-dimensional M-mode imaging of the right ventricular EF (REF), right ventricular SF (RSF), left ventricular EF (LEF), and left ventricular SF (LSF) were performed. Doppler surveys were performed at (1) 10-14 weeks; (2) 15-19 weeks; (3) 20-24 weeks; (4) 25-29 weeks; (5) 30-34 weeks; and (6) 35-40 weeks. The following values were measured: REF, RSF, LEF, LSF, REF/LEF and RSF/LSF. A total of 42 cases were included. The values of REF, RSF, LEF, and LSF for the six gestational time periods were (1) 0.86, 0.49, 0.85, 0.48; (2) 0.84, 0.48, 0.88, 0.51; (3) 0.76, 0.37, 0.84, 0.48; (4) 0.75, 0.37, 0.84, 0.48; (5) 0.76, 0.38, 0.83, 0.47; and (6) 0.77, 0.38, 0.84, 0.48, respectively. The ratios of REF/LEF and RSF/LSF in each gestational time period were: (1) 1.04, 1.11; (2) 0.95, 0.92; (3) 0.95, 0.90; (4) 0.94, 0.90; (5) 0.94, 0.92; and (6) 0.92, 0.89, respectively. After 20 weeks' gestation both the EF and SF of the right ventricle decreased. A non-significant change in the LEF and LSF was observed throughout pregnancy. A decreasing trend in the REF/LEF and RSF/LSF ratios during pregnancy was noted.