The sheep fetus has sufficient placental flow reserves or compensatory responses to maintain adequate gas exchange during a 1-hour, 20 mmHg maternal pneumoperitoneum. Laparoscopic surgical procedures may prove to be a safe alternative to laparotomy during pregnancy.

Variability in the fetal heart rate is known to be a sign of fetal well-being, and yet the origins of the variations remain unclear. This study incorporated the nonlinear analytic techniques of phase-space reconstruction and dimensional analysis to 12 normal heart rate tracings obtained from fetal scalp electrodes of fetuses in labor. Phase-space attractors were constructed with the method of time delays and showed characteristics consistent with those of nonlinear chaotic systems. Dimensional analysis resulted in three distinct groups being identified. Results indicate that control of the fetal heart rate may be modeled as a nonlinear or chaotic system, and analytic techniques borrowed from the physical sciences are useful in exploring heart rate variability. That different groups could be distinguished among qualitatively similar heart rate tracings may lead to understanding of discrepancies between evaluation of the monitor tracing and neonatal outcome.

Transmission time of atrial pressure into the venous circulation increases with distance from the atrium and decreases with volume loading. Umbilical venous velocity pulsations derive from atrial pressure changes transmitted in a retrograde fashion.

Umbilical venous Doppler velocity pulsations developed after fluid administration and were associated with increases in inferior vena cava peak pressure. These findings suggest that umbilical venous pulsations develop when fetal venous pressures are elevated.