Hypocalciuria and Hypertension in Pregnancy: A Prospective Study

In 138 women in the third trimester of pregnancy, those with pre-eclampsia showed a significantly reduced 24-hour urinary calcium excretion (2.94 mmol/24 h) in comparison with those with essential hypertension (5.32 mmol/24 h) or with pregnancy induced hypertension (PIH) alone (4.97 mmol/24 h). There was no difference in either calcium intake or plasma calcium level between these groups. Normotensive women showed no change in calcium excretion with increasing gestation (within the third trimester). We were unable to demonstrate a reduction in urinary calcium excretion in pre-eclamptic women prior to the onset of hypertension and renal involvement. We conclude that a reduction in 24-hour urinary calcium excretion discriminates between women with pre-eclampsia (with renal involvement) and those with essential hypertension or PIH alone. The timing of this reduction offers little promise of an early screening test to identify those with hypertension who will develop renal involvement.