Intrapartum fluid administration and sodium concentration in maternal and umbilical cord plasma

Maternal and umbilical cord plasma sodium concentrations at delivery following routine labour ward management in uncomplicated pregnancies were studied. Three groups, each consisting of 16 patients, were recruited during labour. One group received 5% dextrose solution for administration of oxytocin. Another group received Hartmann's solution with epidural analgesia. The remaining group received no fluid (controls). There was no difference in the maternal and umbilical cord plasma sodium concentrations between patients who received 5% dextrose solution or Hartmann's solution and controls. Mild hyponatraemia (plasma sodium between 131 and 134 mmol/l) was common in all groups of mothers but severe hyponatraemia (less than 130 mmol/L) was rare. Similarly transplacental hyponatraemia was uncommon. There was no correlation between maternal plasma sodium concentration and the amount of fluid given. It was concluded that intravenous 5% dextrose solution and Hartmann's solution given during labour would not lead to significant hyponatraemia in the mother or fetus if the volume given was less than 0.6 litre.