BJOG Release: Drinking Too Much Water Is Bad During Childbirth

Main Category: Pregnancy / Obstetrics
Also Included In: Pediatrics / Children's Health
Article Date: 30 Jan 2009 - 5:00 PDT

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New research to be published in BJOG: An International Journal of Obstetrics and Gynaecology reveals the potential dangers of high water intake during childbirth.

Hyponatraemia (too little sodium in the blood, plasma sodium < 135 mmol/l) occurs when a person consumes too much water. The common symptoms are: irritability, headaches, nausea and vomiting. If left unchecked, without excess water being removed, swelling of the brain (cerebral oedema) occurs resulting in convulsions and at its most severe, coma.

287 pregnant women in Kalmar County Hospital, south-east Sweden were studied from January -June 2007. Women were allowed to drink freely during their labour. Blood samples were collected on admission and after delivery. Cord blood samples were also taken and analysed to see if the effects could be detected in the baby

In the study, 61 women had taken more than 2,500 millilitres of fluid during their labour, and 16 of them were found to have hyponatraemia ≤ 130 mmol/l. Researchers found that a reduction in plasma sodium levels correlated with a longer second stage of labour. Also, maternal plasma sodium was also observed to be lower in women following instrumental vaginal delivery and emergency caesarean section for failure to progress

Hyponatraemia is difficult to diagnose during labour as the initial symptoms may be confused with the symptoms of pre-eclampsia. Hyponatraemia has been found to be a common condition following labour because the ability to deal with fluid overload is reduced during labour.

There are no guidelines on the safe levels of water intake during labour in the UK (nor in several other European countries or Australia) and some previous studies have shown that higher fluid intake improves obstetric outcome. However, from their study findings, researchers warn that as water load tolerance falls during labour, and increased fluid volumes can cause hyponatraemia, women should not be allowed to drink excessively during labour.

Dr Vibeke Moen, from the Department of Physiology and Pharmacology at the Karolinska Institute said "Our study investigated the hypothesis that women are at high risk of developing hyponatraemia during labour.

"We found moderate hyponatraemia in 26% of the women with a total fluid intake of more than 2.5 litres. In labours exceeding eight to 10 hours, a fluid intake of 300 millilitres per hour was sufficient for the development of hyponatremia, indicating that tolerance to a water load is markedly diminished during labour. Women with the lowest concentration of plasma sodium also had prolonged second stage labour, and were more often delivered instrumentally or by emergency caesarean section for failure to progress.

"We conclude that hyponatraemia is not uncommon following labour, and is potentially harmful, but is also easily avoidable. Women should not be encouraged to drink excessively during labour, and the policy of liberal fluid administration should be questioned. Future research should investigate the possibility that hyponatraemia may influence uterine contractility."

Professor Philip Steer, BJOG editor-in-chief said, "Although it is important to replenish ourselves with liquids, previous studies on athletes have shown that there can be problems with drinking too much water too quickly, even if you are feeling thirsty.

"At one time, a myth became prevalent that drinking lots of water each day was a healthy habit. However, recent research shows clearly that in general, one can trust one's natural body messages, and that we only need to drink more when we feel thirsty. Drinking too much water can be as harmful as drinking too little.

"As this research shows, it is important for doctors and midwives to note how much fluid is drunk by women who are in, or about to go into labour, in order to avoid hyponatraemia."

Notes

BJOG: An International Journal of Obstetrics and Gynaecology is owned by the Royal College of Obstetricians and Gynaecologists (RCOG) but is editorially independent and published monthly by Wiley-Blackwell. The journal features original, peer-reviewed, high-quality medical research in all areas of obstetrics and gynaecology worldwide. Please quote 'BJOG' or 'BJOG: An International Journal of Obstetrics and Gynaecology' when referring to the journal.

Reference

"Hyponatremia complicating labour-rare or unrecognised? A prospective observational study." BJOG 2009;116:564-573.

Royal College of Obstetricians and Gynaecologists

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