About 300 ml (10 oz) a day more than usual when pregnant, and about 600–700 ml (20–24 oz) more when breastfeeding, according to the European Food Safety Authority. For a 65 kg woman that's roughly 2 450 ml of drinks a day in pregnancy and 2 850 ml while breastfeeding. Your midwife's or doctor's advice always comes first.
How much water should you drink when pregnant or breastfeeding? It's one of the questions I took most care with when I built Hydra's goal, because the people asking it deserve a careful answer. This article covers healthy pregnancies and healthy adults, and keeps to what the health bodies actually recommend. It isn't medical advice: if you have a condition, or your midwife or doctor has given you a different number, follow them.
What the recommendations say
Two health bodies set the numbers most apps and articles use, and they broadly agree.
- EFSA (European Food Safety Authority), 2010: for adult women, about 2.0 litres of total water a day, from drinks and food together. In pregnancy, about 300 ml more. When breastfeeding, about 600–700 ml more.
- Institute of Medicine (US), 2005: for adult women, about 2.7 litres of total water a day, of which about 2.2 litres from drinks. When breastfeeding, about 0.7 litres more from drinks.
Notice that the totals include food. EFSA expects about 20–30% of your water to come from what you eat, and the US figure assumes about 20%. Hydra's goal is for drinks only, so food is extra on top. I explain how that works in whether food counts towards your water intake.
Why Hydra adds 300 ml and 700 ml
For pregnancy the choice was easy: EFSA says about 300 ml, so Hydra adds +300 ml.
For breastfeeding, EFSA gives a range of 600–700 ml, and I chose the top of it, +700 ml. Two reasons. The US recommendation lands on about the same number, 0.7 litres more from drinks. And while you're breastfeeding, part of the water you drink leaves every day with the milk you make, so I'd rather the goal not fall short. When two recommendations agree on a number, I'd rather use it than split the difference.
Both extras are added only when sex is set to Female, and they sit on top of everything else in your goal: weight, activity and climate still count the same.
Worked examples
Hydra's goal starts from 33 ml per kg of body weight (about 0.5 oz per lb), then adds or removes a little for sex, activity, climate, and pregnancy or breastfeeding. The total is rounded to the nearest 50 ml. If you want the details of the base formula, I wrote them up in how much water to drink for your weight.
Take a woman who weighs 65 kg (about 143 lb), is slightly active and lives in a temperate climate:
| Stage | Calculation | Daily goal | In ounces |
|---|---|---|---|
| Usual | 65 × 33 = 2 145 | 2 150 ml | about 73 oz |
| Pregnant | 2 145 + 300 = 2 445 | 2 450 ml | about 83 oz |
| Breastfeeding | 2 145 + 700 = 2 845 | 2 850 ml | about 96 oz |
In everyday terms, pregnancy adds a bit more than one glass of water a day, and breastfeeding adds about three. That's it. You don't need to carry a gallon jug around.
The other parts of the goal still apply. Say the same woman is breastfeeding and it's a 30 °C (86 °F) day: Hydra adds 500 ml for the heat, so 2 145 + 700 + 500 = 3 345, rounded to 3 350 ml (about 113 oz). Hot days matter for everyone, and I go through them in how much water to drink in hot weather.
How to set it in Hydra and in the calculator
In Hydra's Settings, set sex to Female. The Pregnancy or breastfeeding option then appears: choose Pregnant or Breastfeeding, and the extra is added to your goal. Tap Goal ⓘ on the Today screen to see how your goal is built, line by line, so you always know where each number comes from. When the stage is over, set it back and the goal follows.
The personal goal is part of Hydra Pro; the free version uses a standard 2 500 ml goal. If your midwife or doctor gives you a specific amount, you can also set the goal by hand and Hydra will track against that instead.
On the website, the water intake calculator works the same way: choose Female, and a Pregnancy or breastfeeding choice appears with the same +300 and +700 ml. It uses the same formula as the app.
Making the extra easier
An extra glass or three a day sounds simple, but it's easy to forget when your days are full. A few things that help:
- Keep a glass or bottle where you spend the most time, and one where you feed the baby.
- Spread drinks across the day instead of catching up in the evening.
- Count all your drinks, not only water. Most drinks count towards your goal; which ones suit you in pregnancy is a question for your midwife or doctor.
I collected more habits like these in how to drink more water every day.
When to talk to your midwife or doctor
The numbers above are for healthy pregnancies and healthy adults. Please ask your midwife or doctor, and follow what they tell you over anything here or in any app, if:
- you have a heart, kidney or other medical condition, or have been told to limit or increase fluids;
- you're being sick a lot, can't keep fluids down, or feel unwell;
- you're unsure how much is right for you.
One more thing applies to everyone: more is not always better. Drinking very large amounts in a short time can dilute the sodium in your blood, which is dangerous. Spread your drinks over the day and don't force yourself far past thirst.
What to take from it
- Pregnancy: about 300 ml (10 oz) more a day than usual.
- Breastfeeding: about 600–700 ml (20–24 oz) more. Hydra uses 700 ml.
- For a 65 kg woman: about 2 150 ml usually, 2 450 ml pregnant, 2 850 ml breastfeeding.
- Heat and activity still add on top.
- Your midwife's or doctor's advice comes first.
A goal that knows you're pregnant or breastfeeding
Hydra adds the extra water to your goal, shows you each part of it, and counts every drink by what your body keeps. Free on iPhone and Apple Watch.
