ULTRASONOGRAPHIC ASSESSMENT OF FETAL GROWTH - COMPARISON BETWEEN HUMAN AND OVINE FETUS

OBJECTIVE: Our purpose was to evaluate the rate of ovine fetal growth for several body parameters by serial ultrasonographic measurements an d to compare them with analogous data in the human fetus. STUDY DESIGN : Forty-three ewes with singleton gestations were studied. Four parame ters were measured: biparietal diameter, abdominal circumference, femu r length, and tibia length. Ultrasonographic examinations were perform ed weekly from 50 to 138 days of gestation (term 147 days). Quadratic regression analysis was used to describe each data set. RESULTS: The b iparietal diameter showed a significant deceleration of its growth rat e. The abdominal circumference showed a linear growth pattern. Both fe mur and tibia revealed a significant acceleration of the growth rate. CONCLUSION: The ovine fetal growth pattern is different from that obse rved in the human fetus, in which all four parameters show deceleratio n of the growth rate in late gestation. In comparison to the ovine, th e human fetus reaches similar abdominal circumference and femur length values at term, but in a gestational period that is twice as long. In sharp contrast to abdominal circumference and femur length growth, th e biparietal diameter has a similar growth rate in both species. Thus the human fetus has a slower rate of somatic growth and its greater bi parietal diameter at term results from the longer gestational period.