“Physiologic” intracellular acidosis in pregnancy

To investigate acid-base homeostasis in pregnancy, we used phosphorus 31 nuclear magnetic resonance spectroscopy to measure intracellular pH in erythrocytes from nonpregnant (n = 33) and third-trimester pregnant women (n = 22). Intracellular pH was lower in pregnant compared with nonpregnant controls (7.23 ± 0.15 vs 7.29 ± 0.012, p = 0.003). We hypothesize that this “physiologic” intracellular acidosis of pregnancy potentiates oxygen-hemoglobin dissociation and oxygen delivery across the placenta.