In ninety-four Dutch nulliparous women the effects of a low-Na diet in pregnancy on blood pressure, energy and nutrient intake, Ca metabolism, Zn and Mg status and body composition were studied longitudinally. The women were randomly divided into an intervention group (n 41), which used a low-Na diet (mean urinary Na excretion 61 mmoV24 h) from week 14 of pregnancy until delivery and a control group (n 53; mean urinary Na excretion 142 mmoV24 h). No effect of the diet on blood pressure was observed. The use of a low-Na diet resulted in significantly reduced intakes of energy, protein, carbohydrates, fat, Ca, Zn, Mg, Fe and cholesterol. However, the women on the low-Na diet appeared to be able to adapt quite well to the reduced intake since Ca, Zn and Mg homeostasis was maintained. In the case of Ca and Mg this was probably due to the observed reduced urinary excretions of these nutrients. Non-significant reductions in weight gain (1-5 kg) and fat-mass gain (0.9 kg) over pregnancy were found in the women on the low-Na diet. No significant effects of the diet on birth weight or placental weight were observed. Pregnancy: Sodium: Blood pressure: Nutritional statusThe present study was part of a multicentre controlled randomized study, in which the prophylactic effect of a low-Na diet during pregnancy on hypertensive disorders was evaluated (B. J. A. Van Buul, E. A. P. Steegers, G. D. Van der Maten and T. K. A. B. Eskes, unpublished results). Thus far not much consideration has been given to the (patho)-physiological consequences of a change in Na intake for mother and fetus. Therefore, each centre also studied different possible side-effects of the low-Na diet. In the present study the results for the additional variables studied at the hospital Groot Ziekengasthuis are described. The aim of the study was to investigate, besides an effect on blood pressure, the effects of a low-Na diet in pregnancy on maternal energy and nutrient intake, Ca metabolism, Zn and Mg status, weight gain and body-fat storage. Since there are indications that nutrition, mineral and trace element status and body composition are related to pregnancy outcome, in affecting these variables a low-Na diet may have implications for the health of the mother and fetus (Institute of Medicine, 1990
SUBJECTS AND METHODS
Study designNinety-four nulliparous women visiting the antenatal clinic of the hospital Groot Ziekengasthuis were studied longitudinally from early pregnancy until 6 weeks postpartum. Pregnancies were dated using the first day of the last menstrual period. After baseline measurements, at week 13 of pregnancy, the women were randomly assigned (by closed envelope system) to an intervention group (I-group), which used a low-Na diet from week 14 of pregnancy onwards until delivery, and a control group (C-group), which continued its ad libitum dietary intake. Blood pressure, heart rate, food consumption, blood and urinary analyses, body weight and skinfold thicknesses were measured during pregnancy and post-partum. In addition, infant birth...
