BACKGROUND Obesity in pregnant women is a serious health issue. Invasive monitoring devices are rarely used in pregnancy due to their risks; however, assessment of cardiac function is often required in these women. Transthoracic echocardiography offers advantages but may be technically difficult to perform. Our aim was to determine the feasibility of transthoracic echocardiography and to quantify left ventricular function and structure using transthoracic echocardiography in obese pregnant women. METHODS Fifteen obese but otherwise healthy pregnant women (body mass index >30 kg/m(2)), were compared with 40 healthy non-obese pregnant women. Echocardiography was performed according to American Society of Echocardiography recommendations. RESULTS Test completion with key haemodynamic data were obtained in 100% of women. Gestational age (Mean ± SD) was similar between groups (36 ± 5 weeks). Compared with non-obese pregnant women, obese pregnant women had elevated mean arterial pressure (88 ± 6 vs. 81 ± 8 mmHg, P=0.003), increased left ventricular mass (162.8 ± 35.4 vs. 130.8 ± 21.0 g, P=0.008) but similar cardiac output (4417 ± 890 vs. 4109 ± 595 mL/min, P=0.230) and diastolic changes (mitral valve E/se' > 8 in 33% vs. 15% of patients, P=0.26). Septal tissue Doppler indices in obese pregnant women were s' 9.1 ± 1.9 cm/s, e' 11.6 ± 2.6 cm/s, a' 8.1 ± 2.7 cm/s. Tei index was reduced in both groups (0.49 ± 0.12 vs. 0.42 ± 0.09, P=0.05). CONCLUSIONS Transthoracic echocardiography was used to delineate haemodynamics in obese pregnant women. Mean arterial blood pressure and left ventricular mass were increased in obese pregnant woman. The incidence of diastolic impairment and reduced myocardial performance were similar between groups.