ALBUMIN EXCRETORY RATE IN NORMAL AND HYPERTENSIVE PREGNANCY

1. The purpose of this study was to determine whether the 24 h urinary albumin excretory rate was increased in the third trimester of normal pregnancy or in pregnant women with hypertension who had 24 h urinary total protein excretion within the normal range. 2. Twenty-four hour urinary creatinine and albumin excretions were determined prospectively in 26 nonpregnant and 115 pregnant women in their third trimester (40 in normal pregnancy, 38 with mild preeclampsia, 20 with severe pre-eclampsia, 17 with essential hypertension) in whom urinary total protein excretion was normal. Both the urinary albumin excretion rate and the urinary albumin/creatinine ratio were compared among the groups. The clearance of albumin relative to that of creatinine was also calculated in the hypertensive women and in 14 of the non-pregnant women and nine of the normal pregnant women. 3. The twenty-four hour urinary albumin excretion Fate was similar in non-pregnant [8(5-10) mg/day; median (interquartile range)] and normal pregnant [7(6-10) mg/day] women. Women with essential hypertension [6(4-16) mg/day] and mild preeclampsia [7(4-10) mg/day] had a urinary albumin excretion rate similar to that of normal pregnant women. Women with severe pre-eclampsia had an urinary albumin excretion rate increased [13(7-32) mg/day] compared with other groups (P<0.05). The clearance of albumin relative to that of creatinine was elevated significantly only in women with severe pre-eclampsia compared with normal pregnant women (0.00054 versus 0.00012; P<0.05). Blood pressures were similar among all hypertensive groups. The upper limit of the urinary albumin excretion rate was 20 mg/day in normal pregnant women, similar to that in non-pregnant women. 4. Urinary albumin excretion is unchanged in the third trimester of normal pregnancy, but is increased in women with features of severe pre-eclampsia who have normal total urinary protein excretion. This is not fully explained by a reduction in glomerular filtration rate nor by different systemic blood pressures, and probably reflects enhanced glomerular capillary permeability, possibly with altered maximum renal tubular reabsorption capacity for albumin.