Fluid Balance during Labour: A Review

A randomized controlled trial of the effect of intrapartum intravenous fluid management on breastfed newborn weight loss

OBJECTIVE

To determine the effect of conservative versus usual intrapartum intravenous (IV) fluid management for low-risk women receiving epidural analgesia on weight loss in breastfed newborns.

DESIGN

A randomized controlled trial.

SETTING

A tertiary perinatal center in a large urban setting.

SAMPLE

Women experiencing uncomplicated pregnancies who planned to have epidural analgesia and to breastfeed.

METHODS

Healthy pregnant women were randomized to receive an IV epidural preload volume of <500 mLs continuing at an hourly rate of 75-100 mL/h (conservative care) or an epidural preload volume of ≥500 mLs and an hourly rate >125 mL/h (usual care). The primary study outcome was breastfed newborn weight loss >7% prior to hospital discharge. Secondary study outcomes included breastfeeding exclusivity, referral to outpatient breastfeeding clinic support, and delayed discharge. Other outcomes were admission to the neonatal intensive care unit and cord blood pH <7.25.

RESULTS

Two hundred women participated (100 in the conservative care and 100 in the usual care groups). Forty-eight of 100 infants in the usual care group and 44 of the 100 infants in the conservative care group lost >7% of their birth weight prior to discharge, p < 0.52 RR 0.92 [0.68-1.24].

CONCLUSION

A policy of restricted IV fluids did not affect newborn weight loss. Women and their care providers should be reassured that the volumes of IV fluid <2500 mLs are unlikely to have a clinically meaningful effect on breastfed newborn weight loss >7%. Exploratory analyses suggest that breastfed newborn weight loss increases when intrapartum volumes infused are >2500 mLs. Care providers are encouraged to consider volumes of IV fluid infused intrapartum as a factor that may have contributed to early newborn weight loss in the first 48 h of life.

NPO during labor. Is there any scientific validation?

Maternal death from pulmonary aspiration of gastric contents has virtually disappeared in the United Kingdom. The one case documented in the most recent triennial report was a woman with multiorgan failure in intensive care and is probably not relevant to the current debate [1]. Although not so well documented, other Western countries seem to be experiencing the same decline in maternal death from this cause. At the same time, the burden of proof is falling increasingly on obstetric anesthesiologists as obstetricians and midwives demand that NPO policies should be rejected, unless anesthesiologists can prove that they are necessary. Without any proof of benefit, many midwives actively encourage eating in women who do not really want to eat. A hospital manager who wants to divert money to other areas of health care might make the same argument about employing less experienced--and therefore cheaper--anesthesiologists or nurse anesthetists on the labor floor. Although no self-respecting obstetric anesthesiologist would accept such a situation, there is still no randomized controlled trial that proves that experienced anesthesiologists reduce maternal mortality. Similarly it is difficult for a mother to comprehend the negligible risk of pulmonary aspiration during labor while her care providers insist that it would be more dangerous for her to cross a busy road! Against a background of conflicting advice from midwives and medical practitioners, the mother is likely to eat if she feels so inclined. Pulmonary aspiration is a rare complication, so even if a light diet in labor became acceptable, it is likely that it would take many years for a subsequent increase in maternal mortality to become apparent. It would be disappointing if mistakes made by a previous generation had to be relearned in the twenty-first century. Increasingly, media-controlled pressure groups dictate health fashions, and the physicians frequently can only stand on the sidelines and advise. Most obstetric anesthesiologists agree that a rigid NPO policy in labor is no longer appropriate and that at least water or ice chips should be allowed. Current evidence suggests that solids and semi-solids should be avoided once a woman is in active labor or requests analgesia. The appropriate advice is to allow a carefully audited introduction of isotonic drinks. These drinks seem to be an effective medium for providing calories while minimizing any increase in gastric volume, and such a policy would be unlikely to reverse the reduction in aspiration that has been achieved over the past 50 years.

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.