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“Plenty of IV Fluids May Make Childbirth Safer, Easier,” enthuses the Philadelphia Inquirer, over a systematic review (a “study of studies” on a particular topic) finding that infusing IV fluids at 250 mL per hour instead of the usual 125 resulted in shorter labors and fewer cesareans. Let’s summarize the review (Ehsanipoor 2017) and then count the ways in which the review makes sense only to medical-model practitioners.
The reviewers pooled data from 7 trials comparing IV fluid rates of 250 mL/hr (593 women) versus 125 mL/hr (622 women). All participants were 1st-time mothers who began labor spontaneously with one baby at 36 weeks or more gestation and who were at low risk for complications. Women in the higher flow rate group had fewer cesareans (13% vs. 18%) overall, fewer cesareans for progress delay (5% vs. 8%, 5 studies, 1215 women), and shorter mean labor duration by about an hour (6 studies, 1155 women). Although numbers are small (254 women total), in the two studies also permitting fluids by mouth the increased IV flow rate had no effect on cesareans (10% vs. 11%). No differences were found for maternal fluid volume overload (fluid in the lungs) (0 vs. 0.2%), inflammation of the fetal membranes (chorioamnionitis) (10% vs. 10%), postpartum hemorrhage (undefined) (3% vs. 4%), or newborn admission to intensive care (4% vs. 3%).
What’s Wrong with This Picture?
The reviewers start from the premise that IV fluids are required in labor to prevent dehydration. Dehydration is a concern because evidence from sports medicine suggests that dehydration can interfere with muscle function, which theoretically could result in cesareans for delayed progress. It therefore becomes reasonable to medical-model thinkers to ask whether the usual infusion rate of 125 mL/hr is adequate to prevent this and attempt to answer it by conducting studies allocating laboring women to faster infusion rates.
Left out of their reasoning is that IV fluids are only needed because oral fluid intake in labor has been forbidden or restricted, and, in fact, the review finds that IV fluids have no effect on cesarean rate in women allowed free access to oral fluids, which leads its authors to conclude, “No recommendations can be made regarding the optimal rate of fluid infusion for women with unrestricted oral intake. [emphasis mine].” This misses the point. Laboring women allowed oral intake don’t need IV fluids. They can maintain hydration on their own, a fact confirmed by the low cesarean rates in low-risk, 1st-time mothers beginning labor at home or in birth centers (7-13%) (Birthplace in England 2011; Bovbjerg 2017; Hutton 2015; Janssen 2009; Johnson 2005; Rooks 1989; Van der Hulst 2004), all of whom would have had unrestricted access to food and drink.
The rationale for denying oral intake in the first place, we should add, was the belief that it posed a risk of death or serious morbidity from inhaling gastric contents should a cesarean be required. That fear—at least in modern times, with current anesthesia administration techniques and the vast majority of cesareans being performed under regional anesthesia—is unsubstantiated, if it was ever valid in the first place (Dawood 2013).
The reviewers were testing the hypothesis that dehydration plays a role in cesarean rates. None of the trials evaluated dehydration, which means that a major link in their reasoning is missing, but leaving that aside, cesarean rates overall in the 250 mL/hr group ranged from 5% to 19% while the rate in the 125 mL/hr group ranged from 10% to 23%, and cesarean rates for progress delay ranged from 1% to 10% in the high-flow group versus 3% to 16% in the low-flow group despite participants in all studies being low-risk 1st-time mothers who began labor on their own. With this much overlap, clearly, other, more influential, factors were in play, again, confirmed by the much narrower range in rates in similar women in the out-of-hospital birth studies cited above.
No adverse effects were found with the higher IV flow rate, but the number of participants is too small, even when aggregated, to reliably detect a difference in rates between groups (underpowered) of uncommon, but serious complications, a problem aggravated, moreover, by not all trials reporting on all the adverse outcomes included in the review. Having said that, though, a rate that amounts to a 2-liter soda bottle every 8 hours probably wouldn’t precipitate some of the more serious problems of fluid overload in most mothers or babies.
On the other hand, by increasing the baseline fluid load, it still raises concerns about total fluid volume should women have an epidural, which involves administration of a bolus (a large quantity over a short time period) of IV fluid as part of its initiation or the larger flow rates given in preparation for and during a cesarean. Also of concern is the propensity of medical-model practitioners to think that if a 250 mL/hr flow rate is good, an even faster rate must be better.
The review omits other adverse outcomes potentially attributable to increasing IV fluid flow rates probably because the trials didn’t report on them. On the newborn side, these include transient tachypnea (rapid breathing due to fluid in the lungs), although as we said above, an increase isn’t terribly likely with a 250 mL/hr flow rate alone. A bigger concern, though, is an artificially inflated birth weight due to the excess IV fluids accumulated during labor. This is problematic because breastfeeding adequacy is gauged by how long it takes babies to regain their birth weight (Chantry 2011; Noel-Weiss 2011). On the maternal side, it includes breast engorgement, which makes latching on difficult and painful.
Also left off the table are the drawbacks of IVs per se. These include limiting mobility, discomfort, and the negative psychological effects of treating labor as pathologic.
What Is Optimal Practice?
Menticoglou & Hall wrote (2002), “One of the most influential biases in the acquisition of evidence is choice of the question, and the best evidence in answer to the wrong question is useless.” True, the reviewers present strong evidence that a higher IV flow rate is associated with a reduction in cesarean rates, but they asked the wrong question. The right one would have been: “Should we be substituting IV fluids for oral intake?” and the answer to that question is an unequivocal, “No.” As Dawood & colleagues (2013) conclude their Cochrane systematic review on whether routine IV fluids are beneficial:
We need to justify why the policy of “nil by mouth” still permeates current practice. This is especially so since dangers of gastric aspiration have been shown to be virtually eliminated and a concern of the past. Therefore, given that there is no clear evidence of harm associated with unrestricted oral intake perhaps it is time to abandon this policy altogether and to allow women to self-regulate their oral intake during labour.
IV fluids, they go on to say, should be limited to clinical indications. Optimal care, then, dictates free access to food and drink and restriction of IVs to such things as administering medications or replenishing fluids in women unable to keep down liquids.
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