A high water intake can be harmful during childbirth, causing headaches, nausea, vomiting and brain swelling that results in convulsions, according to a new study.
This condition results when hyponatraemia or too little sodium in the blood occurs because of excess water consumption. It causes swelling of the brain (cerebral oedema), triggering convulsions and even coma.
The study is based on 287 pregnant women in Kalmar County Hospital, southeast Sweden, between January and June 2007. They 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.
The study found that 61 women had taken more than 2.5 litres of fluid during labour and 16 of them were found to have hyponatraemia. Researchers found that a reduction in plasma sodium levels correlated with a longer second stage of labour.
There are no guidelines on the safe levels of water intake during labour in Britain (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.
Said Vibeke Moen, from the department of physiology and pharmacology at the Karolinska Institute: "Our study investigated the hypothesis that women are at high risk of developing hyponatraemia during labour."
Philip Steer, editor-in-chief of obstetrics and gynaecology journal BJOG that published the research, said: "...previous studies on athletes have shown that there can be problems with drinking too much water too quickly, even if you are feeling thirsty."