There's a long list of pregnancy symptoms that people talk about openly — the nausea, the tiredness, the bizarre food cravings, the emotional rollercoaster. And then there's constipation, which affects roughly 40% of pregnant women and which almost nobody discusses because, well, it's constipation. It's not glamorous. It's not the kind of thing you bring up at the antenatal coffee morning. But it's real, it's uncomfortable, and at its worst it can make you genuinely miserable in a way that the pregnancy books somehow fail to convey.
I first experienced it around week ten. Having spent weeks six through nine feeling too nauseous to eat much of anything, I'd finally regained my appetite and was enthusiastically eating again — vegetables, whole grains, all the sensible things — and nothing was happening. Days passed. I felt bloated, heavy, irritable. My usually reliable digestive system had apparently decided to take a sabbatical without informing me. I Googled "pregnancy constipation" at 2 a.m. — as one does — and was simultaneously reassured that it was normal and frustrated that "normal" could feel this awful.
What I needed, and what this article provides, is a proper understanding of why pregnancy does this to your body, which remedies actually work (and are safe), and at what point you should stop trying to manage it yourself and speak to your midwife. Because while constipation during pregnancy is common and usually benign, it's also not something you simply have to endure in stoic silence for nine months.
Why pregnancy causes constipation (it's not just diet)
The main culprit is progesterone — the hormone that sustains your pregnancy and also, as a side effect, relaxes smooth muscle throughout your body. Your intestines are lined with smooth muscle, and it's the rhythmic contraction of this muscle (peristalsis) that moves food through your digestive tract. When progesterone relaxes these muscles, peristalsis slows down. Food moves more slowly through your gut, your colon absorbs more water from it as it lingers, and the result is harder, drier stools that are more difficult to pass.
This isn't a malfunction — it's actually an evolutionary advantage. Slower digestion means more thorough nutrient absorption, which benefits your growing baby. Your body is prioritising nutrient extraction over comfortable bowel movements, which is efficient but deeply annoying.
Beyond progesterone, several other factors compound the problem:
- Iron supplements: Prescribed to many pregnant women for anaemia prevention, and constipation is their most common side effect. We'll discuss this in detail later because it's often the tipping point between "manageable" and "miserable."
- Physical compression: As the uterus grows, it physically presses on the intestines, further slowing transit. This becomes more significant in the second and third trimesters.
- Reduced physical activity: Fatigue, nausea, and general pregnancy discomfort often lead to less movement, and physical activity is one of the most effective natural stimulants for bowel function.
- Dietary changes: If nausea has limited your diet to toast, crackers, and plain pasta — the classic first-trimester survival foods — you may be getting significantly less fibre than usual.
- Dehydration: Morning sickness, increased blood volume, and simply forgetting to drink enough water can all contribute to dehydration, which directly hardens stools.
- Stress and anxiety: The gut-brain axis is real, and pregnancy anxiety (which is extremely common) can affect gut motility. Stress tends to divert blood flow away from the digestive system, slowing things further.
The combination of these factors is why pregnancy constipation is so prevalent and why it often doesn't respond to simple dietary changes alone. It's not just that you're eating differently — your entire digestive system is operating under altered hormonal conditions. Understanding this is important because it removes the frustration of "I'm doing everything right and it's still not working." You may be doing everything right. Your hormones are just very good at their job.
How it changes across trimesters
First trimester: Constipation often begins early — sometimes within the first few weeks — as progesterone levels rise sharply. If you're also experiencing morning sickness, the dietary restriction (fewer vegetables, less fibre, more bland carbohydrates) compounds the hormonal effect. Some women who've never had digestive issues suddenly find themselves going days between bowel movements. It's disorienting.
Second trimester: For many women, the second trimester brings some relief. Nausea often subsides, allowing a more varied diet. However, iron supplementation may begin around this time (following blood tests at the booking appointment), and iron can reintroduce constipation just as the hormonal effect was becoming manageable. The uterus is also growing but isn't yet large enough to cause significant compression.
Third trimester: This is typically when constipation is at its worst. The uterus is now large enough to physically compress the intestines, progesterone levels are at their peak, and the physical discomfort of late pregnancy makes exercise less appealing. Many women also experience reduced appetite as the baby takes up space previously occupied by the stomach, which can mean less fibre intake. It's the perfect storm of constipation-promoting factors.
The pattern isn't universal — some women sail through pregnancy with no digestive issues, while others are affected from week five onwards. But knowing that it tends to worsen as pregnancy progresses can help you put preventive strategies in place early rather than waiting until it becomes a problem.
Dietary solutions that genuinely work
Diet is your first line of defence, and it's the one area where you have the most control. The target is simple: more fibre, more fluid, and more variety. But the specifics matter, because "eat more fibre" is the kind of advice that sounds straightforward until you're nauseated and the thought of a salad makes you want to cry.
Fibre — the right kinds:
There are two types of fibre, and both matter for constipation but they work differently:
- Insoluble fibre (wholemeal bread, bran, brown rice, vegetable skins) adds bulk to stools and helps them move through the intestines. It's the "roughage" that grandmothers talk about.
- Soluble fibre (oats, beans, lentils, apples, flaxseeds) absorbs water and forms a gel-like substance that softens stools and makes them easier to pass.
For pregnancy constipation, soluble fibre is often more effective than insoluble fibre, because the problem is usually hardness rather than volume. Insoluble fibre without adequate fluid can actually worsen constipation — it adds bulk to already-dry stools, which is not what you need.
Practical high-fibre additions that even a nauseated pregnant woman can manage:
- Porridge (oats): Excellent soluble fibre, gentle on the stomach, easy to eat in the morning. Add a tablespoon of ground flaxseed for extra fibre and omega-3s.
- Prunes: The original natural laxative. Three to four prunes daily (or a small glass of prune juice) contain sorbitol, which has a mild osmotic laxative effect. They work. Consistently. If you try nothing else from this article, try prunes.
- Kiwi fruit: Two kiwifruits daily have been shown in clinical studies to improve stool consistency and frequency. The enzyme actinidin aids digestion, and the fibre content is substantial for such a small fruit.
- Beans and lentils: Add to soups, stews, or curries. Half a tin of beans adds roughly 7g of fibre to any meal. If gas is a concern (and it often is during pregnancy), introduce them gradually rather than suddenly eating large quantities.
- Wholemeal bread instead of white: A simple swap that adds about 2g of fibre per slice. Over a day, that's significant.
- Fruits with skin: Apples, pears, plums — eat them with the skin on for maximum fibre. Stewed apple is particularly gentle if raw fruit triggers nausea.
The hydration factor
Fibre without adequate fluid is like a sponge without water — it doesn't do what it's supposed to. During pregnancy, your fluid needs increase because your blood volume expands by roughly 50%, and your body is producing amniotic fluid. The NHS recommends drinking 6–8 glasses of fluid per day as a baseline, but during pregnancy — particularly if you're increasing your fibre intake — aiming for 8–10 glasses is more appropriate.
What counts as fluid: water (obviously), herbal tea (most are fine during pregnancy — peppermint and ginger are popular and safe), diluted fruit juice, milk, and soup broth. Coffee and regular tea count toward your fluid intake but are limited during pregnancy (200 mg caffeine per day maximum, which is roughly two mugs of instant coffee or one strong coffee).
The most effective timing for hydration in relation to constipation:
- First thing in the morning: A large glass of warm water (with or without lemon) before breakfast can stimulate the gastrocolic reflex — the natural urge to have a bowel movement after eating or drinking. Warm water is slightly more effective than cold for this purpose.
- With meals: Drinking water with each meal helps fibre do its job. This is particularly important if your meal is high in fibre.
- Regularly throughout the day: Rather than large quantities at once, sip consistently. Keep a water bottle with you. If you find plain water boring, sparkling water, cucumber-infused water, or weak herbal tea provides variety without any drawbacks.
A practical sign that you're drinking enough: your urine should be pale straw-coloured. If it's dark yellow, you need more fluid. During pregnancy, slightly more frequent urination is already inevitable (the uterus presses on the bladder), so the annoyance of extra bathroom trips is not a reason to drink less — it's a reason to accept that this is your life now and to make friends with every public toilet between your home and your workplace.
Movement and exercise
Physical activity stimulates peristalsis. This is well-established in gastroenterology and it applies during pregnancy just as much as at any other time. The challenge is that pregnancy can make exercise feel less appealing — fatigue, nausea, pelvic pain, breathlessness, and sheer physical bulk all conspire against your motivation. But even moderate, low-impact movement makes a measurable difference to bowel function.
Walking: The most accessible and effective option. A 20–30 minute walk after meals (particularly after your largest meal) takes advantage of the gastrocolic reflex and helps move things along. Walking is safe throughout pregnancy unless your midwife has specifically advised against it. It also helps with mood, sleep, and circulation — a genuinely multi-benefit activity.
Swimming: Buoyancy relieves the physical weight of pregnancy while the exercise stimulates bowel function. Many women find swimming more comfortable in the third trimester than any land-based exercise because the water supports the bump.
Prenatal yoga: Certain poses — particularly gentle twists and forward folds — can stimulate the digestive organs. Prenatal yoga classes teach modified versions that are safe for pregnancy. The relaxation component also helps manage stress-related gut dysfunction.
Pelvic floor exercises: A strong, responsive pelvic floor supports effective bowel movements. Pelvic floor exercises (Kegels) are recommended during pregnancy for multiple reasons, and improved bowel function is one of the less-discussed benefits.
The key is consistency rather than intensity. A daily 20-minute walk does more for constipation than an occasional intense workout. Your body responds to regular, predictable movement patterns, and establishing a daily walking habit early in pregnancy pays dividends throughout.
Iron supplements: the hidden culprit
If your constipation became significantly worse after starting iron supplements, this section is for you. Iron is one of the most common causes of medication-induced constipation, and during pregnancy the irony (no pun intended) is acute: iron is prescribed to prevent anaemia, which is important, but the constipation it causes can be severe enough to affect quality of life.
How iron causes constipation: iron supplements — particularly ferrous sulphate, the most commonly prescribed form — are poorly absorbed. Only about 10–20% of the iron you swallow is actually used by your body. The rest passes through your digestive system, where it can irritate the gut lining and slow intestinal motility. It also tends to harden stools. The characteristic black stools during iron supplementation are a visual reminder of how much iron is passing through unabsorbed.
Strategies that help:
- Take iron with vitamin C: A glass of orange juice or a vitamin C tablet alongside your iron supplement improves absorption, meaning more iron gets into your blood and less passes through your gut. This can meaningfully reduce the constipating effect.
- Take iron on an alternate-day schedule: Emerging research suggests that iron absorption is actually better when taken every other day rather than daily. Some midwives now recommend alternate-day dosing for women who struggle with side effects. Ask your midwife about this — it may allow you to get the iron you need with fewer gut symptoms.
- Switch formulations: Ferrous sulphate is the cheapest and most commonly prescribed form, but it's also the most likely to cause constipation. Ferrous fumarate and ferrous gluconate may be better tolerated. Liquid iron supplements are often gentler on the stomach. Spatone — a naturally iron-rich water — is very well tolerated but provides a lower dose, so it may not be sufficient for significant anaemia.
- Don't take iron with tea, coffee, or dairy: These reduce iron absorption, meaning more passes through your gut. Take iron on an empty stomach or with vitamin C for optimal absorption.
- Discuss with your midwife: If constipation from iron supplements is severely affecting your quality of life, tell your midwife. They may adjust the dose, change the formulation, or — if your anaemia is mild — suggest dietary iron sources instead. The goal is adequate iron levels with manageable side effects, and your midwife can help find that balance.
Safe remedies and what to avoid
When dietary changes, hydration, and exercise aren't sufficient — and sometimes they aren't, because hormones are powerful — there are remedies that are considered safe during pregnancy and others that should be avoided.
Safe during pregnancy:
- Lactulose: An osmotic laxative available over the counter. It draws water into the bowel, softening stools. It's considered safe throughout pregnancy and is often the first-line medical recommendation. It can take 24–48 hours to work and may cause bloating initially.
- Fybogel (ispaghula husk): A bulk-forming laxative that works similarly to dietary fibre. It's safe during pregnancy and effective when taken with plenty of water. Take it at a different time from iron supplements to avoid interference with absorption.
- Glycerine suppositories: Safe for occasional use. They work locally by lubricating the rectum and stimulating the urge to evacuate. They work quickly — usually within 15–60 minutes — and don't have systemic effects.
- Prune juice: Contains sorbitol, a natural osmotic agent. A small glass (150 ml) in the morning is a well-established folk remedy that has genuine evidence behind it.
Use with caution (ask your midwife first):
- Senna (Senokot): A stimulant laxative. Some sources consider it safe for short-term use during pregnancy, but others advise caution — stimulant laxatives can cause abdominal cramping, and there's limited safety data for pregnancy. Your midwife can advise whether it's appropriate for your situation.
- Docusate sodium: A stool softener that is generally considered safe but should be discussed with your healthcare provider before use during pregnancy.
Avoid during pregnancy:
- Castor oil: Can stimulate uterine contractions and has been associated with premature labour. Do not use during pregnancy.
- Mineral oil (liquid paraffin): May interfere with the absorption of fat-soluble vitamins (A, D, E, K), which are important during pregnancy. Not recommended.
- Stimulant laxatives (long-term): Regular use of stimulant laxatives (bisacodyl, senna) can cause dependency and electrolyte imbalances. Occasional use may be acceptable under medical guidance, but they should not become a routine solution.
- Herbal laxative teas: Many contain senna or cascara in unregulated doses. "Natural" doesn't mean "safe during pregnancy." If a product doesn't specify its active ingredients and doses, avoid it.
When to speak to your midwife
Constipation during pregnancy is common, but there are situations where it warrants medical attention rather than home management:
- No bowel movement for more than a week despite dietary changes, increased fluids, and gentle exercise.
- Severe abdominal pain or cramping that goes beyond normal pregnancy discomfort.
- Blood in your stool — this may indicate haemorrhoids (very common in pregnancy) or an anal fissure, both of which are treatable but should be assessed.
- Alternating constipation and diarrhoea — this pattern could indicate irritable bowel syndrome (IBS), which can be exacerbated by pregnancy.
- Vomiting alongside constipation — in rare cases, severe constipation can cause a bowel obstruction, which requires urgent medical attention.
- Constipation accompanied by severe pain and fever — seek immediate medical advice.
In general: if constipation is significantly affecting your quality of life, talk to your midwife. They deal with this regularly, they won't be embarrassed (they've heard it all), and they can prescribe solutions that are more effective than over-the-counter options. Suffering in silence is unnecessary and unhelpful.
Frequently asked questions
Is constipation dangerous for my baby?
Constipation itself does not pose a risk to your baby. Your baby receives nutrients through the placenta and is not affected by your bowel function. However, severe straining can contribute to haemorrhoids and pelvic floor strain, which can cause you significant discomfort. The main concern is your wellbeing rather than your baby's safety.
Can straining during constipation cause miscarriage?
No. Straining during a bowel movement does not cause miscarriage. This is a common fear but there is no medical evidence supporting it. The uterus is well-protected and bowel strain does not transmit force to it in any meaningful way. However, excessive straining can contribute to haemorrhoids and should be avoided for your own comfort.
How many prunes should I eat a day for constipation?
Three to six prunes daily (roughly 30–50 grams) is the commonly recommended amount. Alternatively, a 150 ml glass of prune juice in the morning works similarly. Start with three prunes and increase if needed. The sorbitol in prunes acts as a natural osmotic agent — eating too many at once can cause diarrhoea and abdominal cramping, so start conservatively and adjust.
Will pregnancy constipation go away after birth?
For most women, yes. Once progesterone levels drop after delivery (which happens rapidly), normal bowel motility typically resumes within a few days to a couple of weeks. However, the immediate postpartum period can involve temporary constipation due to dehydration during labour, pain medication effects, fear of straining (especially if you've had stitches), and reduced food intake during labour. Keeping up fibre and fluid intake in the first postpartum week helps.
Can I take probiotics for pregnancy constipation?
Probiotics are generally considered safe during pregnancy, and some studies suggest they may help with constipation, though the evidence is not as strong as for dietary fibre. Lactobacillus and Bifidobacterium strains have the most research behind them. They're unlikely to cause harm, but they're also not a guaranteed solution. Think of them as a potential complement to dietary changes rather than a replacement.
Sources