Diarrhoea from pregnancy: understanding your digestive changes

When you find out you’re having a baby, changes to your digestive system are probably not the first thing on your mind. However, diarrhea during pregnancy is surprisingly common, and many people notice shifts in their bowel habits at different stages. Understanding why pregnancy can sometimes be linked with diarrhea, what’s considered normal, and when to seek medical advice can help you feel more prepared. In this article, nutritionist Helen Roach shares insights on the factors that may influence digestion during pregnancy.

Whilst vomiting and ‘morning sickness’ is a well-documented and discussed side effect of pregnancy; there has been less conversation and research around pregnancy-induced diarrhoea¹. Some research suggests around 14%² of pregnant women report episodes of it but anecdotally many testify to the fact they have alternated between bouts of constipation³ and diarrhea at times during their pregnancy journey.

Most of us are all too familiar with what diarrhea is and feels like but medically it is defined as loose (sometimes ‘watery) and frequent (three or more a day) bowel movements⁴ and whilst it is rarely dangerous during pregnancy it can nonetheless make you feel pretty unwell and worry about the effect it might have on the baby. So, what is likely to cause pregnancy-related diarrhea, can you prevent it and how you can treat and resolve it safely?

Potential causes of diarrhea during pregnancy

Hormonal changes: Pregnancy itself does not directly cause diarrhea, but hormonal shifts - especially in early pregnancy - can affect digestion. Some people experience constipation, others may notice diarrhea, and some may experience both at different times. Progesterone (the hormone that helps maintain pregnancy) levels continue to rise throughout pregnancy and prostaglandins (hormone-like substances such as oxytocin) also go up. Receptor cells for these hormones in your gastrointestinal (GI) tract appear to sense and react to these hormonal changes by influencing your gut and intestinal motility (the process in which the digestive muscles contract and move food through the GI tract). Progesterone relaxes the muscles of the digestive tract slowing down the transit of food through the intestines (this more commonly results in constipation but in some women, it can cause the intestines to contract differently leading to diarrhea instead)⁵ and elevated prostaglandins can stimulate muscle contractions causing the muscle that lines the bowels to contract and push out ‘waste’ quicker than usual – potentially leading to loose bowels.
Dietary changes: Being pregnant can make you rethink your diet and strive to eat foods such as high fibre vegetables and fruits which may have a laxative effect if you are not used to eating them or as much of them. You may find yourself avoiding foods you usually enjoy and craving others you wouldn’t normally choose. Common cravings include chips, chocolate, cake, fruit, ice lollies, ice cubes, ice cream, fizzy drinks, and spicy foods⁶ - many of which are not always the gentlest on digestion or the most nutrient-dense.
Increased sensitivity to foods: Pregnancy can sometimes make your digestive system more sensitive to certain foods, leading to temporary food intolerances or mild reactions that may affect digestion and potentially lead to gastrointestinal changes like diarrhoea⁷. Foods that were well-tolerated before pregnancy can occasionally cause digestive changes, including looser stools or more frequent bowel movements. Every woman is different, but common food culprits include dried fruits like prunes which can have a laxative effect; spicy or fatty/greasy/spicy foods which can be hard to digest and/or dairy products. Lactose intolerance⁸, a digestive condition where the body can’t break down lactose (a sugar found in dairy produce) is common as pregnancy hormones can reduce lactase enzyme activity leading to symptoms like bloating, flatulence, abdominal cramps and diarrhea.
Stress and/or anxiety: Stress and anxiety are common experiences during pregnancy, as your body adjusts to hormonal, physical, and emotional changes, along with concerns about birth, the baby’s health, and your new role as a parent. Stress can influence the digestive system by triggering the body’s natural “fight or flight” response, which may speed up digestion and alter normal gut function. This can sometimes lead to more frequent bowel movements or looser stools. Stress hormones, such as cortisol and adrenaline, can also affect the muscles in the digestive tract, contributing to temporary changes in bowel habits.
Prenatal supplements: Prenatal vitamin supplements provide essential nutrients to support overall health during pregnancy. In some cases, certain formulations may affect digestion and lead to temporary changes in bowel habits, including looser stools. Switching to a different supplement brand or form may sometimes help with tolerance, though individual responses can vary.
Medical conditions: Having a pre-existing medical gut or bowel condition such as IBS⁹, Crohn’s disease¹⁰ or coeliac disease¹¹ can sometimes make changes in bowel habits, including looser stools, more noticeable during pregnancy.
Viral or bacterial infections: Although diarrhea can be linked to your pregnancy hormones it might not be anything to do with them and could be the result of a viral diarrhea and sickness bug, such as norovirus or viral gastroenteritis¹². It could also be the result of food poisoning and a bacterial infection such as
Salmonella or E. coli. Unpleasant at the best of times, when you are pregnant it can be more alarming but be reassured that it is unlikely your baby will be harmed by the effects of a short-lived stomach bug. Looking after yourself is key though – get plenty of rest, keep your fluid intake topped up by taking regular small sips of water and eat bland, easily digestible foods¹³.

How diarrhea can change in each trimester

First trimester (weeks 1-12) – early on in your pregnancy hormonal shifts can slow down your digestive system often resulting in constipation. Making changes to your diet – such as including more fibre-rich foods like vegetables, however, affect the frequency and consistency of your bowel movements potentially leading to pregnancy-related diarrhea.

Second trimester (weeks 13-26)- Diarrhea is less common during the second trimester, but some people may still notice changes in bowel habits. This can sometimes be linked to food sensitivities, dietary changes, or short-lived digestive upsets such as a stomach bug.

Third trimester (27-birth) - Some people may notice changes in bowel habits, including looser stools, in the later stages of pregnancy. This can be linked to the body naturally preparing for labour, as hormonal changes influence muscles in the uterus, cervix, and rectum. Whilst it might not be pleasant, pre-labour diarrhea is common and can be managed by drinking fluids regularly, eating easily digestible foods and getting plenty of rest when you can.

7 simple ways to support your digestive comfort during pregnancy

Mostly diarrhea just runs its course without the need for any medication (the most common OTC treatment is loperamide hydrochloride, the active ingredient in Imodium but guidance from the NHS is to avoid it¹⁴) and there are simple ways to help yourself through it naturally including:

Record your symptoms using an online tracker – logging what foods, drinks or behaviours (say, stress) appear to trigger your diarrhea can help you to avoid them or manage them.
Replenish fluids lost as a result of diarrhea. Keep yourself well-hydrated by regularly sipping water, herbal teas and/or electrolyte drinks (these help replace fluids and minerals lost through diarrhea and/or vomiting such as sodium and potassium). Avoid coffee or soft drinks such as cola or energy drinks which contain caffeine (this acts as a stimulant, increasing peristalsis or muscle contractions); those containing artificial sweeteners which can have a laxative effect¹⁵ and milk-based drinks as pregnancy hormones can sometimes reduce lactase enzyme activity leading to lactose intolerance symptoms including diarrhea.
Choose foods which are gentle on the digestive system. Many nutrition experts recommend following a BRAT diet (which stands for bananas, rice, apple sauce and toast)¹⁶) – containing foods which are less likely to upset or irritate the gut and may make stools firmer and more solid. However, the latest thinking expands on these options to include more important pregnancy-friendly vitamin and mineral-rich foods that may not be included in the BRAT suggestions. These include starchy foods like potatoes and cooked carrots plus soups that do not contain milk; eggs and live unsweetened natural yogurt (particularly containing live, active cultures of lactobacillus acidophilus).
Include food and drinks which may have an anti-nausea, anti-spasmodic effect such as fresh ginger, peppermint or chamomile tea and/or fennel seeds.
Prioritise rest as although it’s not always easy, but a bout of diarrhea can leave you wiped out and anxious about leaving the house for fear it could happen again. Rest as much as you need to and help to alleviate stress in whatever way works for you.
Support your gut with fibre-rich and fermented foods Eating a variety of fibre-rich and fermented foods can help support a balanced gut environment. Natural sources of fermented foods include unsweetened yogurt, kefir, kimchi, and sauerkraut.
Fibre-rich foods such as onions, garlic, leeks, bananas, and apples provide nourishment for beneficial gut bacteria.
Don’t forget simple and basic hygiene precautions. Wash your hands regularly and keep common areas of the house disinfected to avoid contracting viral or bacterial stomach infections from others.

When to get professional help and advice

Diarrhea during pregnancy is usually not dangerous. However, if it persists or occurs alongside other symptoms, it can sometimes lead to complications such as dehydration. It is important to seek prompt advice from your GP or midwife if you experience diarrhea along with any of the following:

Lasts for 72 hours or more and/or is getting worse.
Is accompanied by additional symptoms including a high temperature, nausea and vomiting.
You are experiencing bloody diarrhea or diarrhea that is becoming increasingly ‘watery’ and contains mucous.
You are experiencing stomach pain and/or dizziness.
You have been in contact with someone who has had a severe stomach bug.
You suspect the diarrhea you are experiencing is a sign that you are going into labour.