How Much Water Do Pregnant Women Need?

The number gets quoted confidently and it counts for less than how you drink it, which is the part I wish somebody had told me.

The commonly cited figure is around 8 to 10 glasses a day, roughly 2 to 2.4 litres of total fluid, increasing in hot weather, with exercise, and while breastfeeding afterwards. It's a reasonable starting point and a poor stopping point, because requirements vary enormously with climate, activity and body size.

A better measure than counting

Urine colour. Pale straw means well hydrated, dark yellow or amber means drink more, and it's immediate, free, and adjusts automatically for a hot day or a long walk in a way that a fixed target can't.

One caveat: prenatal vitamins containing B vitamins can turn urine bright yellow regardless of hydration. If you take them, judge by thirst, energy and how often you're going instead.

Why it counts more in pregnancy

Blood volume is up by close to half, and all of it has to come from somewhere.

• Blood volume increases by roughly 40 to 50 per cent, and that volume needs fluid.
• Amniotic fluid is produced continuously and is affected by maternal hydration.
• Kidneys are processing waste for two, at a higher filtration rate.
• Constipation is extremely common in pregnancy, and fluid plus fibre is the first-line answer.
• Urinary tract infections are more common, and being well hydrated reduces the risk. UTIs in pregnancy need prompt treatment because untreated they can trigger preterm labour.
• Dehydration can cause Braxton Hicks contractions, which is a frequent and avoidable reason for a trip to triage.

Signs of dehydration that deserves acting on

Thirst arrives late in pregnancy, which makes it a poor instrument. These are better.

• Dark urine, or passing urine much less often than usual.
• Headache, dizziness or feeling faint.
• Dry mouth, cracked lips, unusually dry skin.
• Feeling unusually tired or foggy without another explanation.
• Braxton Hicks tightening that eases after you drink and rest.
• In heat: not sweating despite feeling hot, which is a serious sign and needs medical attention.

Drinking when everything makes you sick

First-trimester nausea makes water taste metallic for many women, and the advice to drink more is unhelpful when swallowing is the problem. Practical workarounds:

• Small sips constantly, never a glass at a time. A large volume at once is the most likely to come back.
• Very cold water, or ice chips and ice lollies. Cold suppresses taste and is often tolerated when room-temperature water isn't.
• Add lemon, mint or cucumber. The metallic taste is often the specific complaint, and flavour masks it.
• Sparkling water, which many find easier than still.
• Eat your fluid: watermelon, cucumber, soup, yoghurt. Food contributes a real share of total intake.
• Use a straw, which reduces the amount you smell while drinking.

If you can't keep fluids down at all for more than a day, are losing weight, or are passing very little urine, contact your midwife or doctor. Hyperemesis gravidarum is a medical condition, and it's treatable.

What counts, and what to limit

More things count than most people think. Two don't, and one of them has a daily ceiling to know about. Where exactly the ceiling lies I'm not certain the guidance agrees on.

• Water, milk, decaffeinated tea and coffee, and diluted squash all count. So does the water in food.
• Caffeine should stay under 200mg a day in pregnancy, roughly two mugs of instant coffee, or one filter coffee. Remember that tea, cola, energy drinks and chocolate contribute.
• No alcohol. There's no established safe amount.
• Herbal teas aren't automatically safe in pregnancy; some are advised against. Check specific ones, and don't assume.
• Sports drinks are unnecessary unless you have been vomiting or exercising hard, in which case they're handy.

A note on swelling

Mild swelling of feet and ankles is normal in later pregnancy, and drinking less water doesn't help. It usually makes fluid retention worse. Sudden or severe swelling of the face, hands or feet, especially with headache, visual disturbance or pain below the ribs, needs urgent assessment, because those are signs of pre-eclampsia.

Sources

• NHS. Have a healthy diet in pregnancy
• NHS. Vomiting and morning sickness in pregnancy

This guide is general information, written to help you understand a topic and ask better questions. It is not medical advice and does not replace your own doctor, midwife or paediatrician. Anything that worries you about your baby belongs with them.

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