The Effects of Increased IV Hydration on Nulliparous Women Undergoing an Induction of Labor

The objective of this study is to compare the effects of intravenous fluid rate on the course of labor in nulliparous patients who are undergoing labor induction and have an unfavorable cervix. The primary hypothesis is that an increased rate of intravenous fluids will shorten the length of labor in patients undergoing induction with an unfavorable cervix.

Exercise physiology has shown that increased fluid intake and replacement can improve skeletal muscle performance in prolonged exercise. Labor is a physically demanding process that is essentially an "exercise" of the uterus, where uterine contractions of varying strength and dilation lead to thinning and dilation of the cervix and to eventual delivery of the infant. It has logically been theorized that, as with any exercise, improved hydration and delivery of carbohydrates to uterine smooth muscle can help optimize the contractions needed during labor. Conversely, dehydration is believed to result not only in decreased uterine perfusion (due to decreased intravascular volume), but also in reduced delivery of nutrients and elimination of waste products from the contracting myometrium.

Inadequate maternal hydration has been postulated to be a contributing factor to prolonged or dysfunctional labor, in which uterine contractions are not sufficiently strong or are inappropriately coordinated to cause adequate cervical dilation and effacement. Even in patients who completely dilate, sufficient voluntary and involuntary muscle effort is required during the second stage of labor to achieve a vaginal delivery. Prolonged labors can not only lead to increased hospitalization cost, but also to increased risks of cesarean delivery for indications such as "failure to progress," chorioamnionitis (intrauterine infection), and postpartum hemorrhage. Establishing techniques to optimize the length and duration of labor has therefore been an area of particular research interest.

To date, several randomized, controlled studies have demonstrated that with higher intravenous (IV) fluid rates, there is a decreased frequency of prolonged labor and possibly a decreased need for oxytocin in patients who present in active labor. One of these studies was performed here at Long Beach Memorial by Garite et al under IRB approval and supervision. Importantly, a systematic review of these studies by the Cochrane Collaboration in 2013 demonstrated that increased intravenous fluid rates (250mL/hr vs 125mL/hr) appears to shorten the time to delivery and the cesarean delivery rate in patients who present in active labor.

The rate of induction of labor has increased dramatically in recent years, from 9.5% in 1990 to 22.1% in 2004. Women undergoing an induction of labor (whether elective or medically indicated) represent a distinct population from those who present in active labor, not only with regards to their baseline characteristics, but also with regards to their labor course and maternal and neonatal outcomes. There have been no studies thus far investigating the use of increased intravenous hydration in patients undergoing induction of labor, as previous studies have focused on patients who present in active labor. The objective of this study is therefore to determine the effect of increased intravenous hydration in nulliparous patients undergoing an induction of labor on length of labor, mode of delivery, and other maternal and neonatal outcomes.

Eligibility Criteria:
Inclusion Criteria:

* Pregnant
* ≥ 18 years of age
* Singleton gestation
* Nulliparous
* Vertex presentation
* Gestational age ≥ 36 weeks
* Bishop score ≤ 6
* undergoing induction of labor

Exclusion Criteria:

* Multiparous
* Preeclampsia at admission
* Gestational or chronic hypertension
* Non-vertex presentation
* Multiple gestation
* Chorioamnionitis at admission
* Intrauterine growth restriction (\<10th percentile)
* BMI \> 50
* Presence of uterine scar
* Participation in any other research protocol involving induction of labor
* Nonreassuring fetal heart rate tracing at admission