Atrial natriuretic peptide and atrial size during normal pregnancy.

Plasma atrial natriuretic peptide (ANP), right and left atrial areas and the diameter of the left atrium were studied serially during normal pregnancy and at 6 weeks post partum in 21 nulliparous women. Concentrations of ANP in plasma were significantly elevated during mid-pregnancy. Thereafter ANP levels were not significantly different from those at 6 weeks after delivery. All atrial measurements were significantly increased in the third trimester of pregnancy, but none was significantly correlated with the plasma ANP concentrations. This might point at an altered mechanism of ANP secretion, which may be part of a physiological adaptive process to sustain the hypervolaemia of pregnancy.