Pregnancy brings plenty of changes to the body, and while morning sickness, fatigue, and food cravings tend to get most of the attention, changes in bowel habits can be just as noticeable. Some people suddenly find themselves going to the bathroom less often, while others notice that their stools have become harder or that a bowel movement requires more effort than it used to. These changes can feel unexpected, particularly when they appear before the pregnancy has begun to show.

So, when does constipation start in pregnancy? For some women, it can begin during the first trimester, sometimes as early as the first few weeks, when hormonal changes are already affecting the digestive system. Others may not experience constipation until the second or third trimester, when the growing uterus and changes in daily routines can place additional demands on digestion. Some people, meanwhile, go through pregnancy without experiencing significant constipation at all.

There isn't a particular week when pregnancy constipation is expected to begin, and its timing can vary considerably from one person to another. Understanding how digestion changes throughout pregnancy can help explain why bowel movements may become less frequent, harder, or simply different from what you're used to.

TL;DR - When Does Pregnancy Constipation Start? A Trimester-by-Trimester Guide:

Constipation can begin during the first trimester, sometimes within the first few weeks of pregnancy.
Rising progesterone levels can slow intestinal movement early in pregnancy, even before the uterus has grown significantly.
Constipation may first appear or become more noticeable during the second or third trimester.
Pregnancy constipation doesn't always mean going several days without a bowel movement; harder stools and increased straining are also common features.
Changes in hormones, physical activity, eating patterns, and iron supplementation can all influence bowel habits during pregnancy.
Not everyone experiences constipation, and its severity can fluctuate throughout the pregnancy.

How Early Can Constipation Start in Pregnancy?

Constipation can develop surprisingly early in pregnancy, sometimes before many of the more visible physical changes have begun. During the first trimester, the body undergoes substantial hormonal adjustments, and these changes affect more than the reproductive system.

One of the most important hormones involved is progesterone, which rises during pregnancy and helps support the developing pregnancy by relaxing smooth muscle tissue. Smooth muscle is also found throughout the digestive tract, where coordinated muscular contractions help move food and waste through the intestines. As progesterone levels increase, intestinal movement may become slower, allowing stool to remain in the colon for longer periods. A Canadian Family Physician review notes that rising progesterone and reduced levels of the hormone motilin both increase bowel transit time during pregnancy.

The longer stool spends in the colon, the more water can be absorbed from it, which may leave it firmer and more difficult to pass. This helps explain why someone who previously had regular bowel movements might begin noticing harder stools or longer intervals between bathroom visits during the early weeks of pregnancy. If you're curious how digestion speed and transit time work in general, we cover it in a separate guide.

However, the relationship between pregnancy hormones and constipation isn't identical for everyone. Some people notice digestive changes almost immediately, while others continue having their usual bowel movements well into pregnancy.

There is no specific gestational week that marks the beginning of pregnancy constipation, and experiencing it early doesn't necessarily mean it will continue throughout all three trimesters.

Can Constipation Start Before You Know You're Pregnant?

Because hormonal changes begin early, constipation can sometimes appear before a person has confirmed their pregnancy. Someone who normally has a bowel movement every morning, for example, might notice that they're suddenly going every other day or that their stool feels unusually firm.

This can happen around the same general period when other early pregnancy symptoms, such as fatigue, breast tenderness, or nausea, begin to develop, although the timing varies.

It's important to remember, however, that constipation is extremely common outside pregnancy as well. Changes in eating habits, travel, stress, hydration, and everyday routines can all affect bowel movements, which means constipation on its own isn't a reliable sign of pregnancy.

Even when it appears alongside other early symptoms, the change in bowel habits doesn't reveal whether pregnancy is the underlying cause. What it does illustrate is that digestion can respond to hormonal fluctuations long before the physical changes associated with later pregnancy become obvious.

Constipation During the First Trimester

The first trimester, which extends through the end of week 13, is often when pregnancy-related digestive changes first become noticeable.

During these early months, progesterone levels rise substantially, and the resulting changes in intestinal movement can affect both the frequency and consistency of bowel movements. Someone who previously passed soft, formed stools every day may begin noticing that their bowel movements are less predictable or that their stool has become drier and more compact.

At the same time, early pregnancy can bring nausea, changes in appetite, and a shifting relationship with food. Meals that once seemed appealing may suddenly become difficult to tolerate, while certain foods may be eaten more frequently simply because they're easier to manage.

These changes can alter the amount and type of material moving through the digestive tract, adding another layer of variability to bowel habits.

For some people, constipation during the first trimester is relatively mild, appearing as an occasional skipped bowel movement or slightly harder stool. For others, it becomes a more persistent source of discomfort, particularly when bloating and abdominal fullness occur alongside it.

The important distinction is that early pregnancy constipation doesn't always involve a dramatic reduction in bowel movement frequency. Sometimes the first noticeable change is simply that passing stool requires more effort than it did before.

Constipation During the Second Trimester

By the second trimester, which generally covers weeks 14 through 27, some of the early symptoms of pregnancy may begin to settle, but digestive changes can continue.

Progesterone remains elevated, meaning the hormonal influences on intestinal movement don't disappear once the first trimester ends. At the same time, the uterus gradually increases in size, changing the amount of space available within the abdomen.

Although the uterus is not necessarily the main reason for constipation at this stage, the combination of hormonal effects, physical changes, and altered daily habits can make bowel movements feel different.

This is also a period when some people begin taking iron supplements or iron-containing prenatal vitamins, which can contribute to firmer stools and reduced bowel movement frequency. Not everyone experiences this effect, but it is a familiar feature of pregnancy-related digestive changes. The same review in Canadian Family Physician lists increased vitamin supplementation, such as iron and calcium, among the contributing factors.

For women who experienced constipation early in pregnancy, the second trimester may bring a continuation of the same pattern, although symptoms can also improve or fluctuate. Others may notice constipation for the first time during these middle months, despite having relatively regular bowel movements earlier.

Rather than following a predictable progression, constipation often changes alongside the many other adjustments taking place during pregnancy.

Constipation During the Third Trimester

During the third trimester, beginning at week 28, the physical changes associated with pregnancy become increasingly pronounced, and constipation may remain present or become more noticeable.

As the uterus grows, it occupies more space within the abdomen and can contribute to pressure on surrounding structures, including parts of the digestive tract. The University of Rochester Medical Center similarly describes how pressure from the pregnancy on the rectum and intestines can interfere with digestion and bowel movements, alongside hormone changes that may slow digestion. Hormonal influences on intestinal movement also continue, so the digestive system is responding to both physiological and mechanical changes.

Daily activity may change during these final months as well. Walking, sleeping comfortably, and maintaining familiar routines can become more challenging, and these shifts may indirectly affect bowel habits.

Some women describe a greater sensation of abdominal fullness during late pregnancy, although it can be difficult to distinguish between the feeling of constipation, ordinary pregnancy-related pressure, and bloating.

For others, bowel movements remain relatively consistent throughout the third trimester, demonstrating once again that pregnancy doesn't produce the same digestive experience in everyone.

Constipation can persist until delivery, but it isn't inevitable, and there is no universal pattern in which symptoms steadily worsen as pregnancy progresses.

What Does Constipation Feel Like During Pregnancy?

Constipation is often described as having fewer bowel movements than usual, but frequency is only one part of the experience. A person can continue going to the bathroom regularly and still notice that their stools have become unusually hard or difficult to pass.

During pregnancy, constipation may involve several overlapping changes. Stool can appear dry, compact, or divided into smaller lumps, while bowel movements may require more straining than before. Some people also experience the sensation that they haven't completely emptied their bowels, even after spending time in the bathroom.

Abdominal bloating and a feeling of heaviness can accompany these changes, making the digestive discomfort more noticeable, particularly later in pregnancy when the abdomen is already undergoing substantial physical changes.

The appearance of stool can provide a useful way to describe these differences. On the Bristol Stool Chart, constipation is commonly associated with Type 1 stools, which resemble separate hard pellets, and Type 2 stools, which have a lumpy, sausage-like appearance.

However, not every episode of pregnancy constipation fits neatly into one category, and the experience may involve changes in both stool consistency and bowel movement frequency.

Why Constipation Doesn't Start at the Same Time for Everyone

Although progesterone plays an important role in pregnancy-related constipation, hormones are only one part of the explanation.

People enter pregnancy with different digestive patterns, and those differences can influence how noticeable a change in bowel habits becomes. Someone who has always had relatively infrequent bowel movements may experience pregnancy differently from someone whose usual routine involves passing stool every morning.

Dietary changes, physical activity, hydration, and the use of iron-containing supplements can also contribute to the overall picture. These factors may become more or less relevant at different stages of pregnancy, which helps explain why constipation can appear, improve, or return rather than following one consistent timeline.

Even the way constipation is experienced varies. For one person, the main difference may be going to the bathroom less frequently, while another may notice that stool has become harder despite maintaining the same bowel movement schedule.

This variability is one reason pregnancy constipation is better understood as a common digestive change with several possible contributing factors, rather than a symptom that begins at a particular week and progresses in the same way for everyone.

Does Pregnancy Constipation Come and Go?

Yes, constipation can fluctuate throughout pregnancy, and some women notice periods of relatively normal bowel movements between episodes of harder or less frequent stools.

Because digestion responds to multiple influences, changes in daily routine, eating patterns, and activity levels may affect stool consistency even while pregnancy-related hormonal changes continue.

For example, someone might experience constipation during the first trimester, notice more regular bowel movements during the second, and then encounter similar difficulties again later in pregnancy. Another person may experience the opposite pattern or have only occasional episodes throughout the entire pregnancy.

There is no single progression that defines pregnancy constipation, and the presence or absence of symptoms during one trimester doesn't reliably predict what will happen during the next. Keeping track of your bowel movements can make these shifts easier to see and to describe to your healthcare provider.

Constipation During Pregnancy Can Take Different Forms

Constipation can start as early as the first trimester of pregnancy, sometimes within the first few weeks, when rising progesterone levels begin influencing the movement of material through the digestive tract. However, it can also appear during the second or third trimester, and some people experience little or no constipation throughout pregnancy.

The timing depends on a combination of hormonal changes, individual bowel habits, dietary patterns, physical activity, and other factors that may shift as pregnancy progresses.

Constipation during pregnancy can also take different forms, from less frequent bowel movements to harder stools, increased straining, and a feeling of incomplete emptying. Understanding these variations makes it easier to recognize how bowel habits may change over the course of pregnancy without expecting every trimester to follow the same pattern.

For general ways to keep things moving, see our guide on how to prevent constipation. During pregnancy, it's best to check with your healthcare provider or midwife before taking any medicine or supplement for constipation, as the University of Rochester Medical Center advises. If constipation is severe, painful, or comes with other worrying symptoms, talk to a professional rather than waiting.

Frequently Asked Questions

What week does constipation start in pregnancy?

There is no specific week when constipation begins. Some people notice changes during the first few weeks of pregnancy, while others experience constipation later in the first, second, or third trimester.

Can constipation start at 4 weeks pregnant?

Yes, constipation can occur around four weeks of pregnancy, when hormonal changes are already underway. However, constipation at this stage isn't specific to pregnancy and can occur for many other reasons.

Is constipation common in early pregnancy?

Yes. Constipation is a common digestive complaint during pregnancy, and it can begin in the first trimester as hormonal changes affect intestinal movement.

Can constipation be an early sign of pregnancy?

Constipation may occur early in pregnancy, but it isn't a reliable indicator on its own because changes in bowel habits are common outside pregnancy as well.

Is constipation worse in the first or third trimester?

There is no universal pattern. Some women experience more noticeable constipation early in pregnancy, while others find that it becomes more pronounced during the third trimester. Symptoms can also fluctuate between trimesters.

Can you be constipated even if you poop every day?

Yes. Constipation isn't defined only by how often someone has a bowel movement. Hard stools, straining, and a sensation of incomplete emptying can also be part of the experience.

Does constipation last throughout pregnancy?

Not necessarily. Some people experience constipation for much of their pregnancy, while others notice temporary episodes or periods when bowel movements return to their usual pattern.

Why does pregnancy cause constipation so early?

Rising progesterone levels can influence the smooth muscles of the digestive tract, slowing intestinal movement and allowing stool to remain in the colon longer. These hormonal changes begin early, which helps explain why constipation may appear before the pregnancy becomes visibly noticeable.

When Does Pregnancy Constipation Start? A Trimester-by-Trimester Guide