The Inorganic Plasma Fluoride Concentrations and Its Renal Excretion in Certain Physiological and Pathological Conditions of Man

Fluoride Metabolism in Pregnant Women: A Narrative Review of the Literature

“…Ionic fluoride is the measure of significance for the health sciences and public health, and the one available to participate in biological reactions [11]. Under steady-state conditions (pH = 7.4 and normal hematocrit), ionic fluoride is asymmetrically distributed between plasma and blood cells in a 2:1 proportion [27]. Plasma is the central compartment for the distribution of fluoride.…”

“…Recently, there has been a renewed interest in this topic with studies using maternal plasma fluoride as a biomarker of prenatal exposure. A summary of available reports of plasma or serum fluoride levels in pregnant women [27][28][29][30][31] is displayed in Table 1. From this table, it can be inferred that reported plasma fluoride levels in pregnant women are within the range reported for nonpregnant adults [28]; however, two observations can be made: (1) as in nonpregnant people, maternal plasma/serum fluoride levels seem to be higher in areas with higher levels of fluoride in community fluoridation programs; and (2) fluoride levels seem to be lower compared to nonpregnant women and to decrease towards the end of gestation.…”

“…Furthermore, the changes in the acid-base balance that occur during pregnancy (such as physiologic hyperventilation or the metabolic acidosis associated with cases of gestational diabetes), lead to variations in blood pH that could potentially affect plasma or serum fluoride levels. To rule out the confounding effect of hemodilution in studies assessing plasma fluoride levels in pregnant women, future studies should control for this factor utilizing individual measures of hematocrit and consider gestational age and any condition involving disturbances in the body's acid-base balance [27]. Whether the decrease in plasma and serum fluoride levels observed towards term is an artifact of changes in hemodynamics or the pregnant body's acid-base balance, remains to be determined.…”

“…Keeping these limitations in mind, from Table 3, two observations can be made: (1) urinary fluoride levels in pregnant women seem to be higher with increasing levels of fluoride intake or exposure; and (2) urinary fluoride levels do vary across pregnancy trimesters. In some cases, an observed decrease in urinary fluoride levels in spot urine towards term, has been discussed as evidence of fetal fluoride uptake [66,70]. Nevertheless, unless appropriate methods for the assessment of the urinary excretion of fluoride are used in future studies, whether urinary fluoride levels tend to increase or decrease towards term, and their association with fetal fluoride absorption, will remain unclear.…”