Constipation in Early Pregnancy: Why It Happens & How Early

Constipation in early pregnancy is primarily caused by the sharp rise in progesterone that occurs after implantation. Progesterone is a smooth muscle relaxant — and the digestive tract is lined with smooth muscle that contracts rhythmically to move food and waste through the bowel. When progesterone rises, these contractions slow down significantly, meaning food and waste move through the digestive system more slowly than usual.

This slowing of the digestive tract — known as decreased gastrointestinal motility — is thought to serve a purpose in early pregnancy by allowing more time for nutrients to be absorbed from food and transferred to the developing embryo. The downside, however, is that the longer waste sits in the large intestine, the more water is absorbed from it, making stools harder and more difficult to pass.

Beyond progesterone, several other factors can contribute to constipation in early pregnancy. Reduced physical activity due to fatigue, changes in diet driven by food aversions and nausea, dehydration if fluid intake has decreased, and the iron content of prenatal vitamins are all common contributors. Understanding which factors are at play can help in finding the most effective strategies for relief.

Constipation can begin surprisingly early in pregnancy — as early as 7-14 DPO for some women, around the time of implantation and the initial rise in progesterone. For some women it is one of the first changes they notice, appearing before more commonly discussed symptoms like nausea or breast tenderness.

Because progesterone also rises after ovulation in every non-pregnant cycle, some degree of digestive slowing in the luteal phase is completely normal regardless of whether conception has occurred. Many women naturally experience some change in bowel habits in the week or two before their period. The constipation of early pregnancy tends to be more pronounced and persistent than typical pre-period bowel changes, and does not resolve when a period would normally be due.

For most women, constipation becomes more noticeable in the weeks following a missed period as progesterone continues to rise. It is one of the most consistently reported digestive complaints throughout the first trimester and can persist well into the second trimester for some women.

The experience of constipation in early pregnancy is similar to constipation at any other time — but many women describe it as more persistent and harder to shift than constipation they have experienced before pregnancy. It can be accompanied by significant bloating, abdominal discomfort and a feeling of fullness that adds to the general discomfort of early pregnancy.

Some women describe feeling bloated and uncomfortable for extended periods, with a sense that their digestion has almost completely ground to a halt. Others notice a change in the frequency of bowel movements — going from daily to every two or three days — without necessarily experiencing the straining and discomfort typically associated with constipation.

• Fewer bowel movements than usual — less than three per week
• Stools that are harder, drier and more difficult to pass than normal
• Straining when trying to have a bowel movement
• A feeling of incomplete emptying after a bowel movement
• Abdominal bloating and discomfort
• Cramping or abdominal pain associated with trying to open the bowels
• A general sense of fullness and digestive sluggishness
• Passing small, hard, pellet-like stools

Constipation before a missed period sits firmly in the category of symptoms that are very difficult to attribute to early pregnancy specifically — because it is also a completely normal PMS symptom for many women. Progesterone rises after ovulation in every cycle and slows digestion whether or not conception has occurred.

Many women experience some degree of constipation or change in bowel habits in the week before their period as a normal part of their cycle — driven by the same progesterone that would cause constipation in early pregnancy. This makes it one of the less reliable early pregnancy indicators when considered in isolation.

The most meaningful difference is what follows. PMS-related constipation typically resolves within the first day or two of a period, as the drop in progesterone that triggers bleeding also releases the brake on digestion. Early pregnancy constipation does not resolve with the arrival of a period — because the period does not arrive — and tends to worsen in the weeks that follow as progesterone continues to rise.

Early pregnancy can affect the bowel in several ways beyond constipation alone. Understanding the range of bowel changes that are normal in early pregnancy can help to reduce anxiety about what you are experiencing.

Some women experience the opposite of constipation in very early pregnancy — loose stools or even diarrhoea, particularly in the first few days after implantation. This is thought to be related to the initial prostaglandin response to implantation and the rapid hormonal changes of early pregnancy, and typically settles quickly as progesterone becomes the dominant influence.

Changes in stool colour, consistency and frequency are all common in early pregnancy. Stools may become darker, lighter, harder or softer depending on dietary changes, hydration levels and the effect of prenatal vitamins. As long as there is no blood in the stool and the changes are not accompanied by severe pain, these variations are generally normal.

• Constipation — the most common bowel change in early pregnancy
• Loose stools or diarrhoea in the very early days after implantation
• Changes in stool frequency — less or more often than usual
• Changes in stool consistency — harder or softer than normal
• Increased gas and bloating alongside constipation
• A feeling of incomplete bowel emptying
• Haemorrhoids — can develop or worsen due to straining with constipation
• Abdominal cramping associated with constipation

Understanding when pregnancy-related constipation can realistically begin helps to give context to any bowel changes you are experiencing during the TWW. Here is a rough guide by DPO:

• 1-5 DPO: Any bowel changes at this stage are related to the natural progesterone rise after ovulation, not pregnancy specifically.
• 6-8 DPO: Implantation is occurring and progesterone is rising. Digestive slowing at this stage is a normal luteal phase change in any cycle.
• 9-10 DPO: HCG is rising after implantation. Constipation that feels more pronounced than your usual pre-period bowel changes may be worth noting.
• 11-12 DPO: Progesterone and HCG are both rising rapidly. More significant constipation alongside other symptoms at this stage may be an early sign.
• 13-14 DPO: Around the time of a missed period. Constipation that has not eased as your period would normally be due leans more toward early pregnancy.
• After missed period: Persistent and worsening constipation after a missed period is a well recognised early pregnancy symptom.

Prenatal vitamins are an important part of preparing for and supporting early pregnancy, but they can significantly worsen constipation for many women. The iron content of most prenatal vitamins is one of the most common causes of constipation in early pregnancy — iron supplements are notorious for causing hard stools and digestive discomfort.

If you started taking prenatal vitamins when TTC and are experiencing constipation, the vitamins may be a significant contributing factor. There are a few strategies that can help. Taking prenatal vitamins with food rather than on an empty stomach can reduce digestive side effects. Some women find that taking vitamins in the evening rather than the morning reduces their impact on daytime digestion.

If constipation from prenatal vitamins is severe, it is worth speaking to a doctor or midwife about switching to a different formulation. Some prenatal vitamins use a gentler form of iron — such as iron bisglycinate rather than ferrous sulphate — that is less likely to cause constipation while still meeting nutritional requirements.

One of the complications of constipation in early pregnancy is the development or worsening of haemorrhoids — swollen blood vessels in the rectum or around the anus that can cause discomfort, itching and bleeding when opening the bowels. Haemorrhoids are extremely common in pregnancy and can develop from very early on.

The combination of increased blood volume, the relaxing effect of progesterone on blood vessel walls, and the straining associated with constipation all contribute to haemorrhoid development in early pregnancy. Some women who have never had haemorrhoids before find they develop them in the first trimester.

Managing constipation effectively is the most important step in preventing haemorrhoid development and reducing discomfort if they are already present. Avoiding straining when opening the bowels, keeping stools soft with adequate hydration and fibre, and using gentle topical treatments if recommended by a doctor can all help.

For women going through IVF, constipation in the two week wait after a transfer is extremely common and is directly caused by the progesterone supplementation used in virtually all IVF cycles. Progesterone pessaries, injections and gel all cause the same digestive slowing that drives constipation in natural early pregnancy — often to a significant degree.

Many IVF patients also take iron supplements and additional medications during their cycle that can further worsen constipation. The combination of progesterone supplementation, iron, reduced physical activity due to resting after transfer, and potential dietary changes can make constipation in the IVF two week wait quite pronounced.

Managing constipation during an IVF cycle is important not just for comfort but because significant straining can be uncomfortable after a transfer. Staying well hydrated, maintaining a high-fibre diet and gentle walking are all safe and effective strategies. If constipation is severe, speak to your clinic before taking any laxatives as some are not recommended in the context of IVF.

Managing constipation in early pregnancy is important for comfort and to prevent complications like haemorrhoids. There are several safe and effective strategies that can make a significant difference.

Increasing fluid intake is one of the most important steps. Water helps to soften stools and support normal bowel function. Aiming for at least 8 glasses of water per day — more if you are also experiencing nausea and vomiting — can make a noticeable difference to constipation. Warm drinks, particularly first thing in the morning, can also help to stimulate bowel movement.

Dietary fibre is equally important. Foods high in soluble and insoluble fibre — including fruits, vegetables, wholegrains, beans and lentils — help to add bulk to stools and support normal bowel motility. Introducing fibre gradually rather than suddenly can prevent the bloating and gas that can accompany a rapid increase in fibre intake.

• Increase fluid intake — aim for at least 8 glasses of water per day
• Eat a diet rich in fibre — fruits, vegetables, wholegrains, beans and lentils
• Try a warm drink first thing in the morning to stimulate bowel movement
• Take gentle regular exercise such as walking
• Do not ignore the urge to open your bowels — responding promptly helps
• Avoid straining — take your time and do not rush
• Consider switching prenatal vitamins to a gentler iron formulation
• Prunes and prune juice are a natural and effective remedy for constipation
• Speak to a doctor before taking any laxatives in pregnancy

Many women are understandably cautious about taking any medication in early pregnancy, including over-the-counter remedies for constipation. It is always worth checking with a doctor or midwife before taking anything.

Bulk-forming laxatives such as ispaghula husk — which work by absorbing water and adding bulk to stools rather than stimulating the bowel — are generally considered safe in pregnancy. They work best when taken with plenty of water.

Stimulant laxatives such as senna are sometimes used in pregnancy but are generally recommended only for short-term use and with medical guidance. Osmotic laxatives such as lactulose are also sometimes used in pregnancy. The safest first-line approach is always dietary and lifestyle changes before reaching for medication.

If you are experiencing constipation that is more pronounced than your usual pre-period bowel changes — alongside other possible early pregnancy symptoms — taking a pregnancy test at the right time is the most reliable next step.

The earliest most sensitive pregnancy tests can detect HCG is around 10-12 DPO, but for the most accurate result it is worth waiting until the day of your missed period and testing with your first morning urine. FMU is the most concentrated of the day and gives the best chance of detecting low levels of HCG in very early pregnancy.

If you test and see a very faint line do not dismiss it. A line that appears within the reading window of the test — no matter how faint — is still a positive result. Retest in 48 hours and the line should be noticeably darker as HCG levels continue to rise.

A faint line on a pregnancy test after constipation and other early symptoms is incredibly common — HCG levels are still low in the early days after implantation and the line on a test can be almost impossible to see even when you are genuinely pregnant.

Enhancing your test photo by adjusting brightness, contrast and using a red light filter can make even the faintest lines much easier to see. Saving your tests and comparing them side by side over several days is also hugely reassuring — a line that gets progressively darker confirms that HCG is rising as it should.

ClearLine is an iOS app that uses AI to analyse your pregnancy test photo and detect even the faintest lines. It includes image enhancement tools, a gallery to save and track all your tests over time, and a side by side comparison feature to help you watch the line progression — everything you need to make sense of those early uncertain results.