Gestation‐specific reference intervals for right and left ventricular ejection force from 12 to 40 weeks of gestation

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Abstract
Aim:  Ejection force of the fetal cardiac ventricles has previously been described from 18 weeks of gestation. We aimed to establish gestation‐specific reference intervals for ventricular ejection force (VEF) from 12 to 40 weeks of pregnancy.Material and Methods:  In a cross‐sectional observational study of singleton pregnancies, examinations were performed in 236 women evenly distributed across each week of pregnancy from 12 to 40 weeks. Each mother was scanned once. For the aortic and pulmonary valves, the time to peak velocity (TPV) and the average (TAV) and peak flow velocity in systole (PSV) was measured. For each we averaged values from three consecutive complexes. The outlet valve diameters were measured and the VEF on both the right and left sides were calculated using the formula VEF = (1.055 × valve area × time to peak velocity × TAV) × (PSV/TPV) where 1.055 represents the density of blood. Measurements were repeated in 40 women to assess intraobserver reproducibility and in 19 women for interobserver variability.Results:  We present reference intervals for right and left VEF. We demonstrated that the ventricular force on both right and left sides increases with advancing gestational age.Conclusion:  Fetal cardiac physiology can be studied and Doppler indices reliably measured as early as the late first trimester of pregnancy. Ventricular ejection force and its relationship with fetal growth could be explored in future studies and this may eventually provide better understanding of changes which may predispose to adult cardiac disease.