Bloated, constipated, reflux: what's actually going on with your gut in pregnancy — and what to do about it

April 19, 2026•11 min read

Gut issues in pregnancy are incredibly common. We're talking constipation, bloating, heartburn, reflux (sometimes all at once...). And for most women, the advice they get is frustratingly unhelpful: drink more water, eat more fibre, and you'll be fine.

That advice isn't wrong exactly, but it's wildly incomplete. For a lot of us, the things actually making our gut issues worse are things nobody seems to point out.

So here's what's really going on and the specific changes that can actually make a difference.

First: why does pregnancy do this to your gut?

It's mostly down to progesterone - the hormone that's absolutely essential for keeping your pregnancy going. Progesterone relaxes smooth muscle tissue, which is great news for your uterus (it stops it contracting too early), but this relaxing effect isn't so great for the muscles in your digestive tract.

The result is that everything slows down. Food moves more slowly through your gut, the trapped door between your stomach and oesophagus (the lower oesophageal sphincter) becomes more relaxed, and digestion in general becomes less efficient than it was before pregnancy.

As your pregnancy progresses, the physical pressure of your growing baby adds another layer. By the third trimester, your stomach and intestines are physically compressed upwards, which is why reflux and bloating so often get worse as you get further along.

These aren't random symptoms, they're the direct result of what your body needs to do to grow a baby. Which is annoying, but it does mean there are specific, targeted things you can do to work with what's happening, rather than just waiting it out.

Constipation in pregnancy

This is the big one. Studies suggest 30-40% of pregnant women experience constipation at some point during pregnancy, with the second trimester being the most common time, though it can happen at any stage.

Beyond progesterone slowing gut motility, there's another factor that many women don't know about.

The iron supplement problem

If you're taking a prenatal multivitamin or an iron supplement that contains ferrous fumarate or ferrous sulphate, this could be making your constipation significantly worse. Yet it's one of the most under-discussed causes of pregnancy constipation.

These are the most common forms of iron used in supplements, but they're also the hardest on your digestive system. A large meta-analysis found that ferrous sulphate significantly increases the risk of gastrointestinal side effects compared to placebo. Constipation, nausea, and stomach discomfort are all more common with these forms of iron.

Ferrous bisglycinate is a different form of iron that's better absorbed and much gentler on the gut.

SCIENCE SNIPPET: A systematic review and meta-analysis of RCTs found that ferrous bisglycinate produced significantly fewer GI adverse events in pregnant women compared to other iron supplements, while also being effective at raising haemoglobin levels. A separate randomised trial found that 25mg of ferrous bisglycinate was as effective as 50mg of ferrous sulphate at preventing iron deficiency in pregnancy, with much fewer side effects.

What to do

Check the iron form in your prenatal supplement. If it lists ferrous fumarate, ferrous sulphate, or ferric iron, it may be contributing to constipation. Switching to a supplement containing ferrous bisglycinate (often at a lower dose) can make a real difference. If you're unsure what's in yours, the iron form will be listed in the ingredients.

Fibre and fluid: the detail matters

Yes, fibre helps with constipation. But the type of fibre matters, and how you increase it matters too.

Soluble fibre (found in oats, apples, pears, beans, and lentils) absorbs water and forms a gel-like substance in the gut, which softens stools and makes them easier to pass. This is generally the more helpful form for constipation.
Insoluble fibre (found in wheat bran, wholegrains, and some vegetables) adds bulk and speeds up transit time. Useful in some cases, but if you're not drinking enough water alongside it, it can actually make constipation worse by adding bulk to dry, hard stools.

The key is increasing fibre gradually to avoid gas and bloating and making sure you're drinking enough fluid at the same time. Aim for at least 8-10 glasses of water a day, and more if it's warm or you're active.

It can also help to enjoy specific fruits: kiwi fruit, prunes, and figs have good evidence for constipation relief.

They contain a combination of fibre, sorbitol (a natural sugar alcohol that draws water into the gut), and polyphenols that help with gut motility. Even 2-3 prunes or a couple of kiwi fruits a day can make a meaningful difference.

Magnesium

This is one I recommend regularly, and it has solid research to back it up.

Magnesium works as an osmotic agent, meaning it draws water into the intestines, which softens and stimulates poops - and it's considered safe for pregnancy.

The form of magnesium matters here. Magnesium citrate and magnesium glycinate are the two most useful for constipation.

Both are reasonably well absorbed and gentler on the gut than some other forms. Magnesium oxide is the form most studied in research and is also effective, though it can occasionally cause looser stools at higher doses.

Magnesium is also one of the most commonly low nutrients in pregnancy, and it has benefits beyond your bowels. It's involved in hundreds of processes in the body, including muscle function, blood sugar balance and sleep. So it's a nice dual-purpose addition.

What to do

Look for magnesium citrate or glycinate as a standalone supplement (150-200mg is a reasonable starting dose for constipation support) or check whether your prenatal multi includes it. If you're already taking one that contains magnesium, you may not need to add more separately.

Movement

Gentle movement, even a 20-30 minute walk each day, can help stimulate gut motility. This isn't about exercise intensity - even light activity helps keep things moving. If you're finding movement harder as your pregnancy progresses, even shorter, more frequent walks still help.

Bloating in pregnancy

Bloating is separate from constipation, though the two often happen together. The slowing of the gut means food ferments longer in your gut, producing more gas than usual. This is why bloating can be so persistent during pregnancy.

Meal size is one of the biggest levers

Your stomach is being physically compressed by your growing uterus, and large meals put pressure on a digestive system that's already working more slowly than usual. Smaller, more frequent meals — rather than three large ones — can make a significant difference to both bloating and reflux.

This isn't about eating less overall. It's about spreading the same amount of food across more meals. Aim for 5-6 smaller eating occasions across the day rather than 3 large ones, and try to stop before you feel uncomfortably full.

Foods that can make bloating worse

Some foods are more likely to cause gas and bloating, and while none of them are harmful in pregnancy, it can be worth moderating them if bloating is a significant problem:

Carbonated drinks (including sparkling water)
Cruciferous vegetables like broccoli, cauliflower, and cabbage — nutritious, but high in fermentable fibres
Beans and lentils, especially if you're not used to eating them regularly
Onions and garlic
Sugar alcohols (sorbitol, xylitol) found in some sugar-free products

None of these need to be avoided entirely, and cruciferous vegetables and legumes are genuinely valuable for pregnancy nutrition. But if you're eating large amounts and struggling with bloating, moderating portions of these foods in particular can help.

Eating slowly

Eating quickly causes you to swallow air, which contributes to bloating. Sitting down for meals, chewing food properly, and not rushing can genuinely help (as basic as that sounds!).

Reflux and heartburn in pregnancy

Reflux is one of the most common pregnancy complaints. Around 40% of pregnant women experience reflux symptoms during pregnancy. It tends to increase through the trimesters, from around 26% in the first trimester to over 55% in the third.

The two causes at play are:

the valve between your stomach and your throat pipe becoming more relaxed (thanks again to progesterone), meaning stomach acid can more easily travel back up;
the physical pressure of the growing baby pushing the stomach upward and increasing abdominal pressure.

Practical changes that help

Smaller, more frequent meals. Large meals worsen reflux, because eating a lot at once puts pressure on the trapped door from the stomach and increases the chance of acid coming back up.
Avoid eating right before bed. Try to leave at least 2 hours between your last meal or snack and lying down. When you're upright, gravity helps keep stomach contents where they should be. When you're horizontal, it doesn't.
Elevate the head of your bed slightly. Even a small elevation (using a wedge pillow or raising the head of the bed by a few inches) can help reduce nighttime reflux by keeping gravity on your side.
Identify your personal triggers. Common reflux triggers include fatty or fried foods, spicy foods, citrus, chocolate, coffee, and carbonated drinks. Not everyone is sensitive to all of these, so it's worth paying attention to what makes yours worse and moderating those specifically, rather than cutting everything out.
Eat slowly and chew properly. Eating too quickly can cause you to swallow air and also means more undigested food in your stomach, both of which can worsen reflux.

If lifestyle changes aren't enough

For many women, these changes help a lot, but might not eliminate reflux entirely (especially in the third trimester when the physical pressure is greatest). That's normal, and it doesn't mean you have to just suffer through it.

If your reflux is severe or significantly affecting your sleep and eating, speak to your midwife or GP about whether additional support (such as antacids) is right for you.

A note on probiotics

There's growing interest in whether probiotics can help with pregnancy gut issues, and some early evidence suggests they may support gut movement and reduce constipation. The research here is still developing, but probiotics are generally considered safe in pregnancy, and there's a reasonable rationale for including them - especially if you're taking antibiotics or have had gut issues before pregnancy.

Look for products containing Lactobacillus and Bifidobacterium strains, and ideally a product that's been third-party tested. They're not essential, but they could be a good addition if you want to cover all bases.

The summary

Gut issues in pregnancy are real, they're common, and they're largely driven by progesterone slowing everything down — compounded by physical pressure as your bump grows. The good news is there are specific things you can do that go well beyond the generic 'drink more water' advice.

The most impactful changes for most women:

Check the iron form in your prenatal - switch to ferrous bisglycinate if you're using ferrous sulphate or ferrous fumarate
Add magnesium citrate or glycinate to support bowel movements
Increase soluble fibre gradually and pair it with plenty of fluid
Eat smaller, more frequent meals to reduce pressure on your digestive system
Add kiwi fruit, prunes, or figs to your day for extra constipation support
Leave 2 hours between eating and lying down if reflux is a problem

None of this is about adding complexity to your already full plate. Small, targeted changes (not a complete diet overhaul) are usually all it takes to feel meaningfully better.

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