Isotonic drinks are used by athletes, dancers and runners to support their exercise and recovery because they are portable, easily absorbed sources of energy. Anything that is isotonic has a similar tonicity or tension to body fluids (such as blood plasma) and passes through cell membranes easily to be absorbed and used quickly. Because isotonic drinks are so easily absorbed, they reduce the risk of dehydration, ketosis and the accompanying fatigue and muscle weakness. Makes sense if people are exercising lots – right? Why on earth would you want isotonic drinks in labour?
Labour is an energetically demanding activity akin to exercise and recent research (McDermott et al. 2022) shows that most birthing people felt able and happy to drink, rather than eat, during labour. Using isotonic drinks can help birthing people to maintain their energy and, just as in athletes, reduces risks of dehydration and ketosis. Ketosis is when the body starts to burn fat instead of glucose for energy, because the glucose in food and drinks has all be used or burned through already. Ketosis produces a range of symptoms including fast heart rate, fever, weakness or lethargy and can cause muscles to work inefficiently. During labour the muscles of the uterus contract to move the baby down and out of the birthing person’s body. If ketosis occurs and causes those muscles to work less efficiently labour may slow or even stop. Kubli et al. (2002) showed that isotonic drinks reduced ketosis in birthing people compared to plain water. Other research shows that drinking isotonic drinks makes no difference to rates of vomiting in labour, labour outcomes: rates of instrumental birth, or rates of caesarean/abdominal birth and doesn’t increase gastric volume which may be of concern if special circumstances arise and a general anaesthetic is needed for an emergency delivery (Malin et al., 2006 & Simonet et al., 2019). After exertion, such as labour, blood sugar levels can drop (if sugars haven’t been replenished by eating or drinking) and alongside symptoms of tiredness, hunger and dizziness low blood sugar can have an impact of breast milk production. Using isotonic drinks during labour and in the immediate postnatal period can reduce these symptoms and support breast milk supply. Guijarro Huerta et al., (2015) shows that the act of supporting their own recovery; being able to reduce fatigue and support breastmilk production helps birthing people to feel more satisfied with their birth experience and postnatal recovery. So what is an isotonic drink and how do I get some? The general consensus is that an isotonic drink contains between 30 grams and 40 grams of sugar per litre and up to 1 gram of salt per litre. This ratio seems to be the most effective for absorption hydration and refuelling muscles. There’s little difference to recovery and hydration between using an isotonic drink and plain water if exercising for an hour or under. Labour often lasts longer than an hour though. There is some research that supports the addition of maltodextrin for activities over 2 hours. The sugar in the drink is used in the first two hours, about the time it takes for maltodextrin to be broken down in to usable sugars, the sugars from maltodextrin are used. Maltodextrin isn’t in some shop bought isotonic drinks but is in others. It can be purchased if you wanted to add it to a homemade isotonic drink but it can be expensive and is a highly processed product often from corn or wheat. It’s worth considering if you want to use maltodextrin or drinks that contain it and choosing accordingly. There are pros and cons to each type of isotonic drink:
Shop bought | Homemade | Dissolvable blend |
| | |
Expensive | Inexpensive | Most expensive |
Convenient but heavy, readymade bottles. | Takes time to make, ideally drink within 24 hours. | Portable and convenient: available as portion packs to be added to water. |
May contain extra artificial or synthetic ingredients. | Complete knowledge of all ingredients. | May contain extra artificial or synthetic ingredients. |
Limited flavours. | Can be made with your favourite flavours. | Limited flavours. |
Shop bought examples include Lucozade sport and Powerade – still, not sparkling, often in fruit flavours. Coconut water is also considered an isotonic drink and has shown good rehydration index and blood glucose responses in research. Many isotonic drinks, those mentioned above and others, are available in a wide range of shops. Homemade recipes are readily available across the internet. I’ve included 2 examples here: one based on fruit squash and one based on fruit juice.
Squash based isotonic drink recipe: 100ml fruit squash of choice (not reduced sugar or sugar free version) 400ml water 4 Teaspoons of sugar Pinch of salt
Mix well and refrigerate if preferred. | Juice based isotonic drinks recipe: 250ml fruit juice of choice (fresh or from concentrate) 250ml water Pinch of salt Mix well and refrigerate if using fresh juice. Long life juice can be kept at room temperature. |
You can choose and combine your favourite flavours when making your own isotonic drinks. Some people who experience pregnancy nausea and vomiting may experience labour nausea and vomiting so ginger may be a helpful addition to a homemade isotonic drink. Dissolvable blends are probably the most convenient if you are packing a hospital bag – small portion packs can slip in the side pocket of a bag or in an empty drinks bottle for transport and easily be added to water which will be available in the hospital. You often pay a premium for that convenience factor but health food stores and sporting goods stores will often carry some form of dissolvable isotonic blend, or you’ll be able to purchase them online. The use of isotonic drinks in labour has been researched for over 20 years and the consensus is that isotonic drinks can be useful for labouring people, do not increase risks often associated with carbohydrate intake and general anaesthesia, do not increase vomiting in labouring people and have no adverse impact on labour progress or birth outcome. Definitely something to consider for your forthcoming labour and something I always have on hand when attending families in labour. Any questions or comments please get in touch.
Slu