K E Y W O R D S:

Objectives

Previous studies have shown that high volumes of intravenous fluid have positive effects on the progress of labor. Pregnant women are often told to drink large amounts of water while pregnant and during labor. However, a number of other reports have shown that abundant drinking during labor causes severe and symptomatic hyponatremia in mothers and infants. This prospective observational study tested the hypothesis that hyponatremia has a high prevalence among women in labor by assessing the occurrence of hyponatremia following delivery in 287 pregnant Swedish women at term. Three study groups were analyzed according to the total volume of fluid received during labor as follows: fluid group 1 (Ͻ1000 mL, n ϭ 113), fluid group 2 (1000-2500 mL, n ϭ 87), and fluid group 3 (Ͼ2500 mL, n ϭ 61). The control group was comprised of 26 women who were delivered by planned cesarean section. The study group women were allowed to drink freely during labor, a common practice in Sweden. Two-thirds of the fluids administered during labor were given orally and the remaining one-third intravenously. Maternal blood samples were obtained upon admission and following delivery; samples were also collected from the umbilical artery and vein. The data were subjected to univariate and multivariate logistic regression analysis.Hyponatremia defined as plasma sodium Յ130 mmol/L occurred after delivery in 16 (26%) of the 61 mothers who had been given more than 2500 ml of fluid during labor. With univariate analysis, reduction in plasma sodium concentration was significantly correlated with total fluid volume administered during labor, the duration of labor and oxytocin administration (P Ͻ 0.001 for all). Maternal reduction in plasma sodium was also correlated with longer duration of second stage of labor, instrumental vaginal delivery, and emergency caesarean section for failure to progress (P ϭ 0.002). After multivariate regression analysis, the correlation between hyponatremia and total fluid intake was maintained (P Ͻ 0.001), but the correlation between hyponatremia and oxytocin administration did not persist (P Ͻ 0.072).These findings indicate that high fluid administration during labor places a high proportion of women at risk for significant and potentially life-threatening hyponatremia. The investigators believe that the current policy in most delivery units of allowing laboring women free access to fluids should be re-evaluated.

Transabdominal ultrasound examination can determine the fetal head position before the start of labour, but the position of the head did not predict the course of labour, probably because the fetal head may rotate during labour even after PROM.

Digital assessment of fetal head descent, cervical length and position can possibly be replaced with ultrasound measurements. Dilatation is best evaluated with digital assessment. Combination of these four factors can predict success of labor induction.