Ductus venosus shunting in marmoset and baboon fetuses

Objectives: The increased shunting of blood through the ductus venosus (DV) during stress situations is an important mechanism that ensures fetal survival. Although primate fetuses may serve to study the function of this important venous shunt, the rate of DV shunting has not been determined in non-human primates under normal conditions. Methods: DV shunting was measured in 11 marmoset (eight mothers) and eight singleton baboon fetuses in mid and late gestation using Doppler ultrasound. Results: DV shunting in marmosets was 39 ± 20% (mean ± SD) and 28 ± 8% in baboon fetuses. Umbilical vein (UV) blood volume rate increased significantly in baboons with gestational age (GA) (UV flow volume = -111.8+ 1.6* GA; r = 0.94, P < 0.05) and slightly in marmosets (UV flow volume = -10.37 + 0.13 * GA; r = 0.42, P > 0.05). Both UV diameter (r = 0.84) and the time-averaged mean UV flow velocity in baboons depended on GA (r = 0.8, P < 0.05). Distinct pulsation was found in marmoset fetuses in the UV (pulsatility index (PI) = 1.3 ± 0.9) and the DV (PI =1.9 ± 1.2) with zero blood flow velocity during atrial contraction. Conclusions: A high level of pulsation is observed in the UV in marmoset fetuses. DV shunting in marmosets is higher than in baboon fetuses.