Cardiac growth in staged human embryos--stages from 15 to 23, post-somitic period.

The cardiac growth was studied in 27 human embryos staged in post-somitic period (stages from 15 to 23, Carnegie Institution of Washington). The cardiac volume was determined by morphometric methods (point-counting planimetry on serial sections) and examined relative to gestational age, to crown-rump length and to the embryo body weight. The data were transformed into logarithms and bivariate relations were analyzed according to allometric equations of the form log y = k (log x) + log b. The data were fitted according to 3 techniques: least squares, major axis and reduced major axis. The allometric regressions slopes (k) indicate positive allometry of the cardiac volume relative to the embryonic age and isometry relative to body weight. The present work will be useful when image techniques, as ultrasonography, turn it possible to evaluate quantitatively the embryonic heart.