A computer-based regression analysis served to test the relationship between fetal heart rate (f.h.r.) and gestational age, and the sex difference in this relationship. The regression equation for f.h.r. on gestational age is y (f.h.r.) = 157.9-0.484 (weeks gestation), making possible prediction of the average f.h.r. for various epochs of gestation. A similar analysis for the subjects by sex shows that in early pregnancy the female f.h.r. is higher than that of the male, but the difference is not great and sex predictions on that basis is of limited significance.