Maternal and fetal blood

Hayashi M. 1983. Lead toxicity in the pregnant rat 11. Effects of low-level lead on delta-aminolevulinic acid dehydratase activity in maternal and fetal blood or tissue. Ind Health 21 127-135. 

In pregnant rats not exposed to nickel, maternal and fetal blood concentrations of nickel were 3.8 and 10.6 pg/L, respectively (Szakmary et al. 1995). Twenty-four hours after a single gavage dose of 5.4,... 

The placenta, through which the drugs will pass to the embryo or fetus, will vary in structure at different times in gestation and between species. For example, there may be six layers of cells between maternal and fetal blood in some species (e.g., pig), but in humans,... 

A recent study investigated PBDEs in 21 paired maternal and fetal blood, and 27 breast milk, with most of the samples collected in Guangzhou (Bi et al., 2006). The concentrations of total PBDEs ranged from 1.5 to 17ngg-1 in the samples, and were within the range reported in European samples for a similar population, but lower than the human tissue levels in North America. BDE 47 and 153 were the dominant PBDE congeners in all samples and accounted for 60% of the total PBDEs. 

GIO. Glendening, B. M., Cohen, A. M., and Page, E. W., Influence of pyridoxine on transaminase activity of human placenta, maternal and fetal blood. Proc. Soc. Exptl. Biol. Med. 90, 25-28 (1955). 

In newborn infants, the blood-brain barrier is not fully developed certain chemicals, like lead, and some endogenous substances, like bilirubin, may therefore enter the brain more easily. Like the brain, but for different reasons, the embryo is also very sensitive to exogenous chemicals circulating in the maternal blood. The placenta is the route by which the developing embryo and fetus exchanges with maternal blood. Its main physiological function is to provide nutrients to the fetus and remove its waste products. In humans, only three layers of cells separate maternal and fetal blood and form what has been termed the placental barrier. 

Pregnant Wistar rats inhaled head-only high levels of [" C]-pyrene aerosol on gestational day 17 (Withey et al. 1992). Concentrations of pyrene and metabolites in maternal and fetal blood were elevated 8-fold with a fourfold increase in exposure concentrations. However, pyrene levels in fetal blood were about 10 times lower than maternal blood immediately after exposure. In general, radioactivity increased in fat but decreased in blood, lungs, and liver tissues from 0 to 6 hours postexposure. There was only a small increase in the concentration of radioactivity in fetuses over the whole exposure range compared to maternal levels, suggesting placental transfer or pyrene and its metabolites are limited or that metabolism in fetal tissues is limited. 

Intrahepatic cholestasis of pregnancy is a syndrome of unknown etiology characterized by a 100-fold increase in maternal and fetal blood bile salt levels. Bile salts are produced in both the fetal and maternal liver. The fetus transfers the bile salts across the placenta for disposal. When the function of the maternal gallbladder is slowed, bile salts can accumulate in the liver and bloodstream, ultimately resulting in the classical pruritus symptom. It is believed that pregnancy-related hormones may slow bile salt excretion from the gallbladder. 

E2. Easterling, W. E., Jr., Simmer, H. H., Dignam, W. J., Frankland, M. V., and Naftolin, F., Dehydroepiandrosterone sulfate, 16a-hydroxydehydroepiandroste-rone and 16a-hydroxydehydroepiandrosterone sulfate in maternal and fetal blood of pregnancies with anencephalic and normal fetuses. Steroids 8, 157-178 (1966). 

R17. Roy, E. J., The concentration of estrogens in maternal and fetal blood obtained at Caesarian section, and the effect of hospitalization on maternal blood estrogen levels. J. Obstet. Gynaecol. Brit. Commonwealth 69, 196-202 (1962). 

Twardock AR, Kuo EY-H, Austin MK, et al. 1971. Protein binding of calcium and strontium in guinea pig maternal and fetal blood plasma. Am J Obstet Gynecol 110(7) 1008-1014. 

Experiments that reveal the effects of alcohol on nerve cells of the prenatal developing brain in humans are not feasible, but animal experiments show that exposure of the fetus to a relatively low level of ethyl alcohol in maternal and fetal blood promotes significant changes in the migration of neurons to... 

Relative Resistance to Diffusion of Maternal and Fetal Blood and the Placental Membranes... 

A further consideration is the relative resistance to diffusion offered by maternal and fetal blood and the placental membranes. The total partial pressure difference between maternal and fetal blood is the sum of the pressure difference from the interior of the maternal erythrocyte to the maternal plasma, plus the pressure difference from the maternal plasma across the placental membrane to the fetal plasma, and the partial pressure difference from the fetal plasma to the interior of the fetal erythrocyte. These relations are diagrammed in Figure 1. The reciprocal of the diffusing capacity, the total resistance to diffusion, is the sum of the resistance of the maternal blood, the resistance of the placental membrane, and the resistance of the fetal blood (12). These resistances are depicted in Figure 1 and may be expressed as ... 

The oxygen contents and partial pressures are related by the hemoglobin dissociation curves for maternal and fetal bloods. We used a modified Hill equation (17, 18) ... 

Uneven Maternal and Fetal Capillary Transit Times. The standard values chosen for maternal and fetal blood flow rates are equal. In studying effects of variations of one of the flow rates (15), the maternal and fetal capillary transit times become unequal, and the time steps of the integration, At, do not correspond to the same distance along the capillary on each side. To prevent the integration from getting out of step (diffusion not occurring perpendicular to the membrane), Equation 5 must be modified (14) to ... 

Results Using Human O2 Dissociation Curves and Hemoglobin Concentration. Since no experimental data are available for values of Dp and capillary flow rates in humans, we assumed the same values as for sheep. Hemoglobin concentrations of 12.5 and 15.5 grams/100 ml for maternal and fetal blood were assumed. Data for maternal and fetal human dissociation curves (17) were fitted with least squares to Equation 7 to obtain the constants fci == 1.421, k2 — 0.456, and k3 = 0.373 for maternal blood and kx — 1.302, k2 = 0.464, and k3 = 0.395 for fetal blood. Human 0 values were calculated from data on k c for adult (20) and fetal (44) blood. 

Effect of Varying Fetal Arterial 02 Tension. Placental exchange has usually been considered limited by either maternal and fetal blood flows or by diffusion. The present analysis suggests umbilical arterial p02 (Pf) is a third and very important factor, based on the observation... 

Effects of Changing Maternal and Fetal Placental Blood Flows Together. Figure 13 shows the effects of varying maternal and fetal blood... 

Eddy currents within the maternal and fetal blood stream are neglected. 

Basic Investigation. A lack of experimental data reporting linear velocities and length of flow channels for maternal and fetal streams required that these values be standardized for the present study. Two types of flow variations are possible. The linear velocities of maternal and fetal blood may change in such a way that the ratio of maternal to fetal volumetric blood flow remains constant. Conversely, maternal and fetal linear velocities may change in a way that will alter the maternal to fetal flow ratio. 

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