Sodium-blood pressure interrelationship in pregnancy

In non-pregnant individuals, a strong positive association of sodium intake with blood pressure has been established, but the relationship between sod ium intake and blood pressure in human pregnancy remains obscure up to date . The aim of this prospective observational cohort study was to assess the relationship between urinary sodium excretion las a measure for intake) and blood pressure from the early second trimester onwards throughout pregnanc y. The study group consisted of 667 low-risk women with singleton pregnanci es, of whom 350 were nulliparous and 317 parous. Blood pressure was measure d in a standardised fashion at predetermined intervals from the first anten atal visit prior to 16 weeks gestation until delivery. Urinary sodium excre tion was measured in 24-h urine collections on at least four occasions betw een 16 and 38 weeks gestation. Main outcome measures were the coefficients of correlation between changes in urinary sodium output and changes in bloo d pressure during six different gestational epochs. No significant correlat ions were found between changes in urinary sodium output and changes in blo od pressure, Correlation coefficients were alike for nulliparous and parous women and for different gestational intervals. Prior to 32 weeks gestation , no differences were observed in sodium excretion between women who remain ed normotensive and those who developed gestational hypertension. These res ults suggest that changes in sodium intake are not associated with blood pr essure changes in low-risk pregnant women. Blood pressure increases as obse rved in the second half of normotensive and hypertensive pregnancies are un likely to be caused by changes in renal sodium handling.