CIRCADIAN VARIATION OF URINARY ALBUMIN EXCRETION IN PREGNANCY

Objective The hypothesis was tested that circadian variations in urinary albumin excretion of pregnant women in the third trimester of normal pregnancy are different from nonpregnant individuals. Design Circadian variability in urinary albumin excretion was studied both in pregnant women and in nonpregnant controls either during normal daily activities or in contrast during continuous bedrest with standardised fluid and food intake to study endogenously generated rhythm. Setting Outpatient department and metabolic ward of a university hospital. Main outcome measures Urinary albumin excretion during fixed time periods over the day and the night. Results Both ambulant pregnant and nonpregnant women have circadian rhythm in urinary albumin excretion but pregnant women have, firstly, a higher 24 h urinary albumin excretion, secondly, smaller relative day-night differences than nonpregnant controls and thirdly, in the metabolic ward some pregnant women demonstrate absence of rhythm. Conclusions The higher albumin excretion during pregnancy in 24 h urine collections can largely be explained by a higher excretion during the night, compared with that of nonpregnant women. The day-night difference in urinary albumin excretion of ambulant pregnant women is exogenously determined.