Inorganic Phosphate in the Pathogenesis of Pregnancy-Related Complications

Inorganic phosphate (P(i)) is an essential nutrient that fulfills critical roles in human health. It enables skeletal ossification, supports cellular structure and organelle function, and serves key biochemical roles in energetics and molecular signaling. P(i) homeostasis is modulated through diet, intestinal uptake, renal reabsorption, and mobilization of stores in bone and extracellular compartments. Disrupted P(i) homeostasis is associated with phosphate wasting, mineral and bone disorders, and vascular calcification. Mechanisms of Pi homeostasis in pregnancy remain incompletely understood. The study presented herein examined biological fluid Pi characteristics over the course of gestation. Correlations with gestation age, pregnancy number, preterm birth, preeclampsia, diabetes mellitus, and placental calcification were evaluated during the last trimester. The results support that maternal urinary P(i) levels increased during the third trimester of pregnancy. Reduced levels were observed with previous pregnancy. Amniotic fluid P(i) levels decreased with gestation while low second trimester levels associated with preterm birth. No significant difference in urinary P(i) levels was observed between preeclampsia and controls (8.50 ± 2.74 vs. 11.52 ± 2.90 mmol/L). Moreover, increased maternal urinary P(i) was associated with preexisting diabetes mellitus in preeclampsia. Potential confounding factors in this study are maternal age at delivery and body mass index (BMI)—information which we do not have access to for this cohort. In conclusion, P(i) levels provide clinical information regarding the pathogenesis of pregnancy-related complications, supporting that phosphate should be examined more closely and in larger populations.