Should Intravenous Hydration Be the First Line of Defense with Threatened Preterm Labor? A Critical Review of the Literature

Because intravenous hydration is a commonly used first clinical effort to reduce preterm labor contractions, this review was initiated to determine whether the literature supports the effectiveness of this clinical strategy. An integrated, critical literature review was done by searching medical, nursing, public health, social, dissertation, and governmental databases to identify the studies relevant to this topic. Literature was chosen for review if it contained (1) objective data on the action of hydration on uterine contractility or (2) data on the clinical syndrome of threatened preterm labor. Research with animals has shown that rapid fluid administration blocks the central release of antidiuretic hormone and oxytocin through blood volume expansion, left atrial distention, and the resulting Henry-Gauer reflex, which thus alters uterine activity. Only four studies have been published that examined the effects of hydration for stopping labor. The effect of hydration was not significantly different from that of bedrest or of tocolytics in any of those studies. In all of them, time appears as an uncontrolled covariant. Although the consequences of hypervolemia might be expected to affect uterine contractions, there is no published evidence that pregnancies have been prolonged through the use of hydration. Hydration has rarely been studied as a single therapy in the prevention of preterm delivery. Caution concerning the use of intravenous hydration is advised by many authors reviewed, because if tocolytic drugs are administered after initial intravenous hydration with large amounts of fluids, the risk for pulmonary edema increases.