Reference Ranges for the Size of the Fetal Cardiac Outflow Tracts From 13 to 36 Weeks Gestation

Abstract

Background: Assessment of the outflow tract views is an integral part of routine fetal cardiac scanning. For some congenital heart defects, notably coarctation of the aorta, pulmonary valve stenosis, and aortic valve stenosis, the size of vessels is important both for diagnosis and prognosis. Existing reference ranges of fetal outflow tracts are derived from a small number of cases. Methods and Results: The study population comprised 7945 fetuses at 13 to 36 weeks’ gestation with no detectable abnormalities from pregnancies resulting in normal live births. Prospective measurements were taken of (1) the aortic and pulmonary valves in diastole at the largest diameter with the valve closed, (2) the distal transverse aortic arch on the 3 vessel and trachea view beyond the trachea at the distal point at its widest systolic diameter, and (3) the arterial duct on the 3 vessel and trachea view at its widest systolic diameter. Regression analysis, with polynomial terms to assess for linear and nonlinear contributors, was used to establish the relationship between each measurement and gestational age. The measurement for each cardiac diameter was expressed as a z score (difference between observed and expected value divided by the fitted SD corrected for gestational age) and percentile. Analysis included calculation of gestation-specific SDs. Regression equations are provided for the cardiac outflow tracts and for the distal transverse aortic arch:arterial duct ratio. Conclusions: The study established reference ranges for fetal outflow tract measurements at 13 to 36 weeks’ gestation that are useful in clinical practice.

Reference ranges and Z-scores for fetal cardiac measurements from two-dimensional echocardiography in Asian population

“…Two-dimensional (2D) echocardiography is currently one of the most practical noninvasive methods to measure cardiac structures for fetuses prenatally and children postnatally. Reference values and Z-scores for fetal cardiac dimensions derived from 2D echocardiography are well-established [1][2][3][4][5][6][7][8][9][10][11][12], allowing quantification and comparison of size of cardiac structures in differing subgroups of a disease [13]. In 1990s, several studies on fetal cardiac measurements using B-mode ultrasonography were published, providing regression equations and 95% confidence intervals based on gestational age [1][2][3].…”

Transposition of the great arteries: Fetal pulmonary valve growth and postoperative neo‐aortic root dilatation

“…However, two researchers performed all the measurements. We did not have our own control group and used the normal data of Vigneswaran et al 21 based on a cohort of more than 7000 fetuses. As the semilunar valves were measured in de closed position by Vigneswaran et al 21…”

“…Comparisons between Z-scores of semilunar valve annulus and left ventricular outflow tract measurements at 1 y and last follow-up Significant results are shown in bold (P < .05). Fetal Z-scores based on Vigneswaran et al21 …”

Measuring Up Before Birth

“…If gestational age is known, it can be used to extrapolate the fetal weight; however, it is important to note that fetal size varies with gestational age and that there is a range of normal body sizes in the fetus, a measure with its own innate heteroscedasticity. 2 Undaunted, in this issue of Circulation: Cardiovascular Imaging, Vigneswaran et al 3 from London present "Reference ranges for the size of the fetal cardiac outflow tracts from 13 to 36 weeks gestation: a single-centre study of over 7000 cases" and tackle the problem of providing normal cardiac measurement values in the fetus. The article is an impressive and concise report presenting normal values for aortic and pulmonary valve and aortic and ductal arch diameters over a wide gestational age range in fetuses with no obvious structural abnormalities at fetal echocardiographic assessment or at birth.…”

“…Despite the limitations and the challenges that may lie ahead as the Z-score data presented by Vigneswaran et al 3 enter into general clinical practices, we must take this data seriously. Put simply, this is an extremely large data set in comparison with previously published normative data sets and represents a major contribution to the field of prenatal assessment of the fetal heart.…”