Nitrogen balance of healthy Dutch women before and during pregnancy.

Background: Experimental studies including longitudinal nitrogen balance studies could provide insight into protein metabolism in pregnancy.

Objective: Our aim was to determine the development of nitrogen balance during pregnancy compared with nitrogen balance before pregnancy in women consuming imposed constant diets. We also tracked changes in muscle mass and lean body mass by measuring urinary 3-methylhistidine (3-MeH) and urinary creatinine.