Objectives The authors aimed to establish gestation specific reference intervals for Doppler indices of fetal cardiac function from 12 to 40 weeks of pregnancy.

Methods In a cross-sectional observational study of singleton pregnancies, examinations were performed in 221 women evenly distributed across each week of pregnancy from 12 to 40 weeks. Each mother was scanned once. For the mitral valve, the velocity and duration of the early (E) and atrial (A) waves and interval (a) between E/A complexes was recorded. For the aortic valve, the duration (b), peak and average flow velocity in systole was measured. For each the authors averaged values from three consecutive complexes. Myocardial performance index (MPI) was calculated as (a–b)/b. The aortic valve diameter was measured and the left heart cardiac output was calculated.

Results The authors estimated the mean of a fetal measurement using a cubic polynomial in gestational age. The authors then modelled the absolute residual as a linear function of gestational age to estimate the SD. The authors combined these estimates to generate centile graphs for the outlet peak systolic velocity, time averaged velocity and the aortic valve diameter, mitral E/A ratio, left heart cardiac output and MPI.

Conclusion Fetal cardiac physiology can be studied and Doppler indices reliably measured as early as the late first trimester of pregnancy. Study of development of fetal cardiac function and may eventually provide better understanding of changes which may predispose to adult cardiac disease.