To evaluate whether fetal cardiac measurements can be made in the second tr
imester, we examined a cohort of normal pregnancies between 12 and 18 weeks
' gestation using state-of-the-art ultrasound equipment. We examined this p
opulation longitudinally at intervals of 2 weeks, as well as at 32 weeks' g
estation. From the 4-chamber view we measured the ventricular and atrial ca
vity dimensions, the thickness of the ventricular walls and septum at end-d
iastole, and the annulus dimensions of the mitral and tricuspid valves. Usi
ng a variety of views we also measured the long and cross-sectional diamete
rs of the atria, the aorta, the pulmonary artery and its main left and righ
t branches, the ductus arteriosus, and the superior and inferior veno cavae
. To test the frequency with which measurements could be mode, we divided t
hem into measurements that were clear and easy to define (statistically goo
d), to those that were unclear (statistically bad), or those that were not
measured at all (none). Data were then analyzed by regression analysis, ana
lysis of variance, and covariance. The frequency of reliable measurements v
aried inversely with gestational age. The inflection point for measurements
was approximately at 16 weeks. Data from this longitudinal study were eval
uated agoinst those obtained from our previous study. Because no statistica
l differences were found in measurements between these studies where they o
verlapped, the data were pooled into 1 large group and the mean and SEEs ca
lculated for all variables. Our study demonstrates that with current transa
bdominal imaging, fetal cardiac measurements can be made reliably in normal
fetuses from 16 weeks' gestation onward. The frequency of obtaining data i
n younger normal fetuses suggests it is unlikely that reliable observations
can be made routinely in abnormal fetuses <16 weeks old, although this mig
ht be possible in individual fetuses. (C) 2001 by Excerpta Medico, Inc.