Why drinking water can be deadly for babies

Lauren Fristed and her daughter, Nevaeh, in a photo posted online two days before her death.
Lauren Fristed and her daughter, Nevaeh, in a photo posted online two days before her death. Photo: Facebook

H2O is one of the necessities of life, but for babies a seemingly harmless amount of water can be fatal.

Sadly, that's a fact one US couple learned too late when their 10-week-old daughter died after her mother diluted expressed breast milk with water.

Georgia couple Lauren Fristed and George Landell, who have been charged over the death of baby Nevaeh, told police they watered down bottle feeds as Ms Fristed was not producing enough milk and they could not afford formula. 

Baby Nevaeh suffered hyponatraemia (water intoxication) as a result of drinking the watered-down milk. The condition saw her electrolyte and sodium levels to drop and made her brain swell.

It's not the first time a young baby's life has been put in danger by consuming too much water.

An Australian medical journal last year reported on the case of a six-month-old NSW girl who was hospitalised with life-threatening seizures from consuming too much water after her mother fed her cordial because she could not afford infant formula.

Water intoxication can occur when a person, adult or child, consumes too much water with too few nutrients. The sodium in the blood drops to a dangerously low level as the kidneys cannot excrete enough fluid.

Hyponatraemia can lead to headaches, blurred vision, cramps, swelling of the brain and seizures. 

Paediatric emergency physician Dr Jennifer Anders says babies are at greater risk of water intoxication than others due to their small size, the fact their kidneys are not yet mature and their innate drive to consume fluids. 

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"Even when they're very tiny, they have an intact thirst reflex or a drive to drink," she told Reuters Health. "When they have that thirst and they want to drink, the fluid they need to drink more of is their breast milk or formula."

According to the Australian National Health and Medical Research Council, breastfed babies don't require any additional fluids before six months of age. 

If the weather is hot and parents or carers are worried about dehydration, the baby should be offered additional breast or formula feeds. 

The Australian Breastfeeding Association says a mother's milk has the perfect ratio of food to water to meet their baby's needs.

"It is a living fluid, ever-changing to suit your baby and even in response to the weather," a statement on the ABA website reads. "The first milk your baby gets from a full breast has a low fat content and naturally quenches baby's thirst. [The] later milk has a creamier appearance and satisfies baby's hunger." 

Babies older than six months may be given some water, for example to help with constipation or in hot weather, but it should only be a small amount of water at a time and should not replace milk feeds.

Similarly, older babies who have started eating solids can be offered small amounts of water to help them learn how to use a cup.

Early symptoms of water intoxication which parents and carers should be aware of are a low body temperature (about 36°C or less) and puffiness or swelling in the face. 

Prompt medical attention should be sought if it's suspected a baby or child is suffering from water intoxication in order to reduce the risk of any permanent damage or death.