Maternal (uterine) artery, maternal (uterine) vein, umbilical artery, and umbilical vein blood were obtained simultaneously at the time of 16 cesarean sections. Calcium determinations of these blood plasma samples and those from women in their ninth month of pregnancy suggest either that a calcium “pump” operates in the placenta supplying a higher concentration of calcium to the fetal blood supply than is found in the maternal circulation or that the calcium homeostatic mechanisms operate at different levels in the maternal and fetal organisms. The fluoride concentrations found in the blood plasmas suggest that the placental barrier to the transport of fluoride ion does not operate so as to maintain a difference in concentration of fluoride between the maternal and fetal body fluids.
This work was supported by Grant DE-1850 from the National Institute of Dental Research, National Institutes of Health, Bethesda, Maryland.
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*Original abstract online at https://www.ajog.org/article/0002-9378(70)90571-5/fulltext