Constipation in Pregnancy: Causes and Safe Relief

✓ This content has been medically reviewed by an obstetrician and gynaecologist
Written & medically reviewed by: Op. Dr. Ayşet Jane Özcan, Obstetrics & Gynaecology Specialist
Istanbul Faculty of Medicine · Medical Park Bahçelievler · TJOD and TSRM member
Last updated: 15 October 2026 · Last medical review: 15 October 2026

Constipation is one of the things women mention almost apologetically at the end of an antenatal appointment, after the blood pressure and the scan and the questions about movements. It is worth putting it at the beginning instead. It is extremely common in pregnancy, it is uncomfortable in a way that quietly wears you down, and it is one of the few pregnancy symptoms where a handful of practical changes genuinely make a difference. It is also the starting point for haemorrhoids and anal fissures, both of which are far easier to prevent than to settle once they have arrived.

This page explains why the bowel behaves differently in pregnancy, when the problem usually starts and how long it tends to last, what to change in your diet and daily routine in realistic terms, what to do if your iron tablets are the cause, and which classes of laxative are usually considered and which are usually avoided. It also sets out the symptoms that mean constipation is no longer just constipation and you should be seen. Nothing here replaces a conversation with your own midwife or doctor, who knows your history, your medication and how your pregnancy is going.

Why constipation is so common in pregnancy

The short answer is hormones first, then iron, then pressure. These three overlap, and in most women more than one is at work.

Progesterone slows the bowel

Progesterone rises steadily from early pregnancy and relaxes smooth muscle throughout the body. That is useful for the uterus, which needs to stay quiet, but the gut wall is made of the same kind of muscle. When it relaxes, the rhythmic waves that push contents along become slower and less forceful. Food residue spends longer in the small bowel and considerably longer in the colon. The colon's main job is to reclaim water, so the longer stool sits there, the more water is removed and the harder and drier it becomes. Hard stool is then harder to move, which slows things further. This is the central mechanism, and it is why constipation can appear well before there is any bump at all.

Iron supplements

Iron is the second big contributor and often the most fixable one. Oral iron is poorly absorbed; a large share of each dose passes on into the colon, where it alters the stool and the gut flora and commonly produces hard, dark, difficult stools. Women who were perfectly regular before starting iron frequently date the change to the week the tablets began. It is covered in its own section below, because the answer is almost never simply to stop taking it.

Mechanical pressure later on

The uterus rises out of the pelvis from around 12 weeks, and from the second trimester onwards it increasingly occupies space the bowel used to have. In the third trimester the rectosigmoid region in particular is compressed, and in the last weeks the presenting part of the baby sits low in the pelvis. This does not block the bowel, but it adds resistance at exactly the point where the stool is already hardest.

Everything else that stacks on top

• Nausea and food aversions in the first trimester, which push many women towards plain, low-fibre foods such as crackers, white bread and rice
• Vomiting and reduced drinking, which leave less fluid available to soften stool
• Less physical activity, whether from exhaustion, pelvic pain or advice to rest
• Calcium-containing antacids taken for reflux, which are constipating
• Some anti-sickness medicines, particularly the 5-HT3 class, which slow the bowel
• Pelvic floor muscles that do not relax properly during straining, which becomes more common as pregnancy progresses
• Pre-existing conditions such as constipation-predominant irritable bowel syndrome or an underactive thyroid

None of this means you have done anything wrong, and it is not a sign that something is going badly with the pregnancy. It is a predictable consequence of normal pregnancy physiology.

When it starts and how long it lasts

Most women notice it in the first trimester, often between about eight and fourteen weeks, which surprises people who expect it to be a late-pregnancy problem. Progesterone is already high by then and the slowing of the bowel does not wait for the uterus to grow. For some women constipation is one of the earliest changes they notice, alongside sore breasts and tiredness.

There is usually a second, mechanical peak in the third trimester, when pressure and reduced activity are added to the hormonal effect. In between, many women have a relatively easier second trimester once nausea settles and eating becomes more normal again. Constipation is one of the commonest digestive complaints of pregnancy overall; figures of around one in four pregnant women are widely quoted, and more women than that experience it at some point without necessarily calling it a problem.

It does not usually resolve before the birth, because the cause is still present. What it does do is respond to treatment. The honest framing is that you are managing it for the length of the pregnancy rather than curing it, and that this is entirely reasonable — constipation that is actively managed is usually far less uncomfortable than constipation that is simply endured.

Afterwards, the hormonal effect lifts over the first days to weeks, but the first bowel movement after birth is its own hurdle, particularly after a caesarean, after opioid pain relief, or with perineal stitches. That is dealt with in a separate section further down.

What actually counts as constipation

It helps to be clear about this, because a lot of unnecessary worry comes from expecting a daily bowel movement. The normal range is wide: anywhere from three times a day to three times a week can be normal for a healthy adult, and what matters more is whether your own pattern has changed and whether passing stool is difficult.

Constipation is usually described as some combination of the following, present for several weeks:

• Fewer than three bowel movements in a week
• Hard, dry, lumpy or pellet-like stool
• Straining for a significant proportion of the time
• A feeling that you have not finished, or that something is still there
• A sensation of blockage at the anus
• Needing to press on the abdomen or perineum, or use a finger, to get stool out

You do not need all of these. Two or three, happening regularly, is enough to be worth acting on. If you are passing a soft stool every third day without straining and feeling fine afterwards, you are probably not constipated, and you do not need to chase a daily result.

One further point worth making: abdominal discomfort in pregnancy has several possible sources, and constipation is only one of them. Sharp, short-lived pain low down on one side when you change position is more typical of round ligament pain in pregnancy, which is harmless and unrelated to the bowel. Constipation pain is usually a duller, crampy, shifting fullness, often relieved by passing wind or stool.

Diet changes that genuinely help

Fibre works, but only if you increase it slowly and drink enough alongside it. Added quickly, or added without extra fluid, it reliably produces bloating, wind and sometimes worse constipation — which is why so many women conclude that fibre does not help them.

How much, and over what period

A reasonable target for an adult is around 30 g of fibre a day, and most people start well below that. Increase by roughly 5 g a day each week rather than all at once, and give any change ten to fourteen days before judging it. Your bowel needs time to adapt.

Soluble versus insoluble fibre

This distinction matters more in pregnancy than people realise. Soluble fibre absorbs water and forms a gel, which makes stool softer and easier to pass: oats, barley, linseed, psyllium or ispaghula husk, pulses, pears, apples, citrus and carrots. Insoluble fibre adds bulk and speeds transit: wheat bran, wholemeal grains, skins, nuts and seeds. Both are useful, but if you are bloated and crampy, loading up on wheat bran often makes you feel worse, whereas soluble fibre tends to be better tolerated. If one type is not suiting you, shift the balance before you give up on fibre altogether.

Realistic portions that do something

• Two tablespoons of ground linseed a day, stirred into yoghurt, porridge or soup, with a large glass of water
• A bowl of porridge made with oats rather than instant sachets
• Two green kiwi fruits a day, which is one of the better-studied simple food measures for sluggish bowels
• Four to six prunes, or a small glass of prune juice — prunes contain sorbitol, which draws water into the bowel as well as providing fibre
• A handful of dried apricots or figs
• Pulses added to whatever you are already cooking: lentils in soup, chickpeas in a salad, beans in a stew
• Leaving the skin on apples, pears and potatoes
• Swapping white bread and white rice for wholemeal and brown, gradually rather than overnight

If first-trimester nausea makes all of this impossible, do what you can and come back to it. Keeping food down matters more in those weeks. If you are vomiting repeatedly, losing weight or unable to keep fluids down at all, that is a separate problem — see the section on severe pregnancy sickness — and it needs treating in its own right before anyone worries about fibre.

Fluid is not optional

Fibre without fluid is counterproductive: it bulks the stool without softening it. Aim for roughly eight to ten cups, around two to two and a half litres, of mostly water across the day, more in hot weather or if you are vomiting or exercising. Pale straw-coloured urine is a reasonable everyday check. A warm drink in the morning, taken with breakfast, is worth building in deliberately — it uses a reflex described in the next section.

One practical caution

Large amounts of wheat bran taken at the same time as iron can reduce how much iron you absorb. If you are on iron for anaemia, separate your bran-heavy meal from the tablet by a couple of hours. This is a timing adjustment, not a reason to avoid either.

Movement, timing and toilet position

These cost nothing and are underused. Position in particular can change how much you have to strain, which matters enormously for preventing haemorrhoids and fissures.

Movement

In an uncomplicated pregnancy, around 150 minutes of moderate activity a week is the general recommendation, and for the bowel the best version of that is simply walking — twenty to thirty minutes on most days, at a pace where you could talk but not sing. Swimming and antenatal yoga are good alternatives, particularly if your pelvis or back is sore. Activity stimulates colonic movement and also helps the abdominal muscles work with you when you do go. If you have been advised to limit activity for an obstetric reason, follow that advice and ask what is allowed.

Use the gastrocolic reflex

Eating triggers a wave of colonic activity, strongest in the morning and strongest after the first meal of the day. The practical version: have breakfast, including a warm drink, then allow yourself fifteen to thirty minutes of unhurried time to sit. Doing this at the same time each day trains a pattern. Most people's bowels respond to routine far more than they expect.

Never defer the urge

If you ignore the signal, the stool stays in the rectum, more water is absorbed, and it becomes harder. Repeatedly deferring is one of the quieter causes of worsening constipation, and it is common in pregnancy when you are at work, travelling, or simply uncomfortable moving.

Position on the toilet

This is the single most useful mechanical change. The puborectalis muscle loops around the rectum and keeps it kinked when you are upright; squatting straightens that angle.

• Put your feet on a low stool or a stack of books so your knees are higher than your hips
• Lean forward and rest your elbows on your knees
• Keep your back straight rather than hunched, and let your abdomen relax forward
• Breathe out slowly, or make a low humming or "ssss" sound, rather than holding your breath and bearing down
• Let the abdomen widen and bulge outwards instead of tightening and pulling the pelvic floor up
• Give it five to ten minutes and then stop — leave the phone outside, because long periods sitting and straining are what produce haemorrhoids

Chronic straining over months also loads the pelvic floor, which is already under strain from the pregnancy itself, and is one of the recognised contributors to pelvic organ prolapse later in life. Getting the position right is worth the small effort.

Iron supplements: the commonest treatable cause

If your constipation began within a week or two of starting iron, the iron is almost certainly responsible. The important thing is that the answer is rarely to stop it on your own. Iron is usually being given for a reason — low haemoglobin or low ferritin — and untreated anaemia in pregnancy matters for how you feel, how you cope with blood loss at delivery and how you recover afterwards. Bring it to your midwife or doctor as a problem to solve rather than a reason to quietly stop.

There are several levers, and most women can be made more comfortable without abandoning treatment:

• Check whether you need it at all. Some women are taking iron inside a pregnancy multivitamin without any demonstrated deficiency. Blood tests answer this.
• Check the total dose you are taking. It is common to be on prescribed iron and a multivitamin that also contains iron. Different iron salts also contain very different amounts of elemental iron for the same tablet size.
• Lower the dose, or take it less often. Alternate-day dosing is increasingly used: because the body's own regulatory hormone blunts absorption for about a day after a dose, taking iron every other day can give as much absorbed iron as daily dosing while clearly reducing gut side effects.
• Change the preparation. Different salts and liquid formulations are tolerated differently, and it is very reasonable to try another one.
• Adjust the timing. Iron is absorbed best on an empty stomach, but taking it with a small amount of food is a fair trade if that is what makes it bearable. Vitamin C, such as a glass of orange juice, aids absorption; tea, coffee, milk and calcium supplements reduce it, so separate them by a couple of hours.
• Add a stool softener or osmotic laxative alongside it, rather than fighting the iron. This is a routine and sensible combination.
• Intravenous iron is an option in selected cases, usually where oral iron cannot be tolerated or is not working and there is a reason to correct the anaemia quickly. Your obstetrician will decide whether that applies to you.

One point of reassurance: oral iron turns stool very dark or black. That is expected and harmless. What is not expected is black stool that is sticky and tarry with a strong smell, especially with abdominal pain, dizziness or vomiting — that should be reported the same day, because it can mean bleeding higher in the gut.

Laxatives in pregnancy: what the options are

Before anything else: check with your midwife, doctor or pharmacist before you start a laxative, tell them you are pregnant and how many weeks, and tell them everything else you are taking. The classes below are described so that you understand the conversation, not so that you can self-prescribe. No brand names are given deliberately — what matters is the class and the active ingredient on the box.

The general approach is a stepwise one: diet, fluid, activity and position first; then a bulk-forming agent; then an osmotic agent; then, if needed and usually for a short course, a stimulant. The aim is the lowest dose that produces a soft, easily passed stool, and then tapering off rather than staying on it indefinitely.

Bulk-forming agents

Ispaghula husk, psyllium, methylcellulose and sterculia work essentially as concentrated soluble fibre. They are barely absorbed from the gut, which is why they are generally the first choice in pregnancy. They take two to three days to take effect, must be taken with plenty of fluid, and can cause bloating and wind at first. They are not helpful if the problem is a hard mass already sitting in the rectum.

Osmotic agents

These draw water into the bowel so that stool is softer and the bowel is stimulated by the extra volume. The two commonly used in pregnancy are macrogols, also called polyethylene glycol, and lactulose. Macrogols are not meaningfully absorbed. Lactulose is a sugar that passes unabsorbed to the colon, where bacteria ferment it; this works, but wind, bloating and cramping are common and some women find it unacceptable. Osmotic agents are a reasonable next step when bulk-forming agents alone are not enough, and are commonly the practical mainstay in pregnancy.

Stool softeners and local preparations

Docusate softens stool and has a mild stimulant effect. Glycerol suppositories act locally in the rectum and are useful when the stool is hard and right at the end, which is a different problem from slow transit higher up. Local treatments avoid any systemic effect, which is often an advantage.

Stimulant laxatives

Senna and bisacodyl increase the contractions of the bowel wall. They work faster, and they cause more cramping. In pregnancy they are generally reserved for short courses when osmotic treatment has not been enough, and are used with more caution towards the end of pregnancy. They should be a short-term measure under advice, not a daily habit.

What is usually avoided

• Castor oil — it can provoke uterine contractions and is not used in pregnancy
• Liquid paraffin and other mineral oils — they interfere with absorption of fat-soluble vitamins and carry a risk of aspiration
• Magnesium and phosphate purgatives and repeated enemas — they can shift fluid and electrolytes and are not for routine use
• Herbal "detox", "slimming" or "colon cleanse" teas — many contain anthraquinone stimulants such as senna, cascara or aloe latex at an unknown and unregulated dose. The fact that something is herbal does not make it gentle, and in pregnancy an unknown dose is the problem
• Newer prescription drugs for chronic constipation such as the secretagogues and prokinetics used outside pregnancy — there is not enough safety data, so they are generally not started in pregnancy

If you have already bought something and are unsure, take the packet to a pharmacist and ask. That takes two minutes and is the right use of their expertise.

Haemorrhoids and anal fissure: the usual consequences

These two conditions are the main reason it is worth treating constipation rather than tolerating it. Both are caused or worsened by hard stool and straining, and both are much easier to prevent than to settle.

Haemorrhoids

Pregnancy is a perfect setup: progesterone relaxes vein walls, blood volume is higher, the uterus increases pressure in the pelvic veins, and straining does the rest. Haemorrhoids are swollen vascular cushions inside or at the anus. Typical symptoms are bright red blood on the paper or coating the outside of the stool, itching, a feeling of fullness, or a soft lump that may appear during a bowel movement and go back afterwards. They are very common in the third trimester and in the first days after a vaginal birth, when pushing adds a final insult.

Management starts with the constipation itself. Soft stool is the treatment; everything else is comfort. Warm baths or sitting in a few inches of warm water for ten minutes, cold packs for a swollen external pile, avoiding long periods sitting on the toilet, and not rubbing the area dry all help. There are topical preparations, but several contain steroids or local anaesthetics, so ask which are appropriate for you and use them as short courses rather than indefinitely. Most haemorrhoids improve substantially in the weeks after birth. A pile that suddenly becomes a hard, exquisitely painful lump may be thrombosed, and is worth having looked at promptly because there is a window where it can be treated more easily.

Anal fissure

A fissure is a small tear in the lining of the anal canal, almost always caused by passing a hard stool. The pain is distinctive: a sharp, tearing or burning pain during the bowel movement, continuing for minutes to an hour afterwards, usually with a small amount of bright red blood. What makes it stubborn is the cycle — pain causes the sphincter to spasm, spasm reduces blood flow and delays healing, and fear of the pain makes you put off going, which makes the next stool harder. Breaking the cycle means keeping the stool genuinely soft, often with an osmotic laxative for several weeks, plus warm baths. Your doctor may discuss a topical treatment to relax the sphincter; some of these are used in pregnancy and some are not, which is why it is a conversation rather than a purchase.

When bleeding is not haemorrhoids

Do not assume. Bright red blood on the paper in someone with hard stool is usually local, but bleeding that is dark, mixed through the stool rather than on it, mixed with mucus, heavy, or accompanied by weight loss or a persistent change in bowel habit needs examination and sometimes investigation, regardless of pregnancy. And bleeding from the vagina is a separate matter entirely from bleeding from the back passage: if you are not certain which it is, treat it as bleeding in pregnancy and contact your maternity unit.

Red flags: when constipation is not just constipation

Constipation in pregnancy is usually benign. Occasionally it is the presenting symptom of something that needs urgent attention. Contact your maternity unit or seek urgent medical care, the same day, if any of the following apply.

• No bowel movement and no wind passed, together with vomiting, a swollen abdomen and colicky pain. This combination suggests bowel obstruction. It is uncommon, but it is more likely if you have had previous abdominal surgery or adhesions, and it is a surgical emergency, not something to wait out
• Severe abdominal pain, or pain that is constant rather than coming and going. Constipation pain waves and eases; relentless severe pain does not
• Heavy rectal bleeding, dark blood, or blood mixed through the stool rather than on its surface
• Black, tarry, foul-smelling stool that is not explained by your iron tablets
• Fever, with abdominal pain or a tender abdomen
• Vomiting that prevents you keeping fluids down, or signs of dehydration such as very dark urine, dizziness or passing almost no urine
• Being unable to pass urine at all, particularly in the late first trimester with severe constipation and pelvic pressure. This needs urgent assessment
• New numbness between the legs or around the back passage, new difficulty controlling the bowel or bladder, or new severe back pain with leg weakness. This is rare, but it is an emergency and should go straight to hospital
• Unintentional weight loss, or anaemia that no one can explain
• Vaginal bleeding, leaking fluid, regular painful tightenings before 37 weeks, or any reduction in your baby's movements. These are unrelated to the bowel and always need separate, immediate assessment, however much constipation you have

A useful rule of thumb: constipation should be uncomfortable, not frightening. If the pain has a different quality from anything you have had before, if you are frightened by it, or if you simply cannot settle, that is reason enough to ring. Nobody in a maternity unit minds a call that turns out to be nothing.

After the birth, and while breastfeeding

The first bowel movement after delivery is something a lot of women dread, and the dread itself makes it worse. A few practical things help. Pain relief after a caesarean or a significant tear often includes opioids, which are strongly constipating — many units will offer a laxative alongside them routinely, and it is worth accepting it rather than waiting until you are in trouble. Keep fluids up, particularly if you are breastfeeding, and start gentle walking as soon as you reasonably can.

If you have perineal stitches, supporting the perineum with a clean pad held gently against it while you pass stool reduces the pulling sensation and the fear of tearing something. Stitches do not give way because you open your bowels. Use the same position as before: feet raised, leaning forward, breathing out rather than holding your breath.

Bulk-forming agents, macrogols and lactulose are minimally absorbed and are generally considered compatible with breastfeeding, but confirm with your midwife, pharmacist or doctor for your own situation and for anything stronger. While you are watching your bowels, also keep an eye on what is normal for postnatal bleeding and lochia, since the two are often confused in the first week when everything is sore.

If constipation, straining, leakage of stool or wind, or a feeling of something coming down persists beyond the early weeks, say so at your postnatal check. Pelvic floor physiotherapy helps a great deal with these problems and is far more effective when it starts early.

When to ask for help rather than putting up with it

There is no prize for enduring this. Ask for help, at an ordinary appointment rather than in an emergency, if any of these describe you:

• You have tried increasing fibre and fluid, walking and the toilet position consistently for about two weeks and nothing has changed
• You are straining most times you go, or routinely spending long periods on the toilet
• You have started bleeding, or you have anal pain during and after passing stool
• Your iron tablets are clearly the cause and you are tempted to stop taking them
• You are already using a laxative every day and cannot manage without it
• You are avoiding eating, or restricting fluids, to avoid needing the toilet
• It is affecting your sleep, your mood, or your ability to get through the day

What usually happens at that appointment is straightforward: a few questions about your pattern, stool consistency, diet, fluids and medications, a check of what else you are taking, and often an abdominal examination. An examination of the back passage is sometimes offered if there is pain or bleeding or if a fissure is suspected — it is brief, you can decline it, and it is done with a chaperone if you want one. Blood tests may be arranged if anaemia or thyroid function is in question. From there you will usually leave with a specific plan rather than general advice, and a review point.

Antenatal appointments are the natural place to raise this, and it belongs on the list alongside everything else that is checked during routine pregnancy follow-up. If you tend to forget in the moment, write it at the top of your notes app before you go in. It takes three minutes to raise, and for most women it makes a real difference to how comfortable the rest of the pregnancy feels.

A short summary of what to do first

• Increase fibre slowly over two weeks, favouring soluble sources such as oats, linseed, pulses and fruit
• Drink around two to two and a half litres of fluid a day, more in heat
• Walk twenty to thirty minutes most days if your pregnancy allows it
• Use the gastrocolic reflex: breakfast, a warm drink, then unhurried time
• Feet up on a stool, lean forward, breathe out, do not hold your breath, five to ten minutes maximum
• Never ignore the urge
• Review your iron and any antacids or anti-sickness medicines with your clinician
• If that is not enough, ask about a bulk-forming or osmotic laxative rather than buying something at random
• Raise ordinary bleeding, persistent straining or anal pain at your next appointment, and treat severe pain, heavy or dark rectal bleeding, or no bowel movement and no wind passed with vomiting as reasons to be seen the same day rather than reasons to wait