Fetal cardiac size in normal, intrauterine growth retarded, and diabetic pregnancies.

A total of 177 M-mode echocardiography studies were done on three groups of fetuses at different gestational ages: group I, normally grown fetuses; group II, intrauterine growth-retarded fetuses (IUGR); and group III, fetuses of diabetic mothers. Adjusted for gestational age and for fetal weight, the hearts of fetuses with IUGR were found to have an increased minor axis dimension due to free wall hypertrophy. No ventricular dilation was found in this group. Furthermore, IUGR fetuses have a larger heart proportionally to their body weight, raising the possibility of a "sparing effect" in this particular group. The hearts of fetuses of diabetic mothers were also found to have a significantly larger cardiac size than that of a group of normally grown fetuses. The increase was secondary to free wall hypertrophy, interventricular septal hypertrophy, and right ventricular dilation. This study confirms previous reports about fetal diabetic cardiomegaly and documents the contribution of the different cardiac components to this increase in size. The free wall hypertrophy found in these two groups may occur by different processes, which needs to be further investigated.