Probiotics for pregnant women are live microorganisms that may support digestive health and overall wellbeing during pregnancy. As expectant mothers experience significant physiological changes, including hormonal fluctuations and alterations to gut microbiota, many consider probiotic supplementation to help manage common pregnancy-related complaints such as constipation and bloating. Whilst probiotics are generally considered safe for most healthy pregnant women, UK antenatal care guidelines do not routinely recommend their use. This article examines the evidence for probiotic supplementation during pregnancy, including potential benefits, safety considerations, recommended strains, and when to seek professional advice before starting any supplement regimen.

What Are Probiotics and How Do They Work During Pregnancy?

Probiotics are live microorganisms, primarily bacteria and yeasts, that confer health benefits when consumed in adequate amounts. These beneficial microbes are similar to those naturally present in the human gastrointestinal tract and help maintain a balanced gut microbiome. Common probiotic strains include species from the Lactobacillus and Bifidobacterium genera, which are found in fermented foods such as yoghurt, kefir, and sauerkraut, as well as in dietary supplements.

During pregnancy, a woman's body undergoes significant physiological changes, including alterations to the immune system and gut microbiota composition. Hormonal fluctuations, particularly increased progesterone levels, can slow gastrointestinal motility, leading to common complaints such as constipation and bloating. The maternal microbiome also plays a role in establishing the infant's initial microbial colonisation during birth and through breastfeeding.

Probiotics work through several mechanisms during pregnancy. They compete with pathogenic bacteria for nutrients and adhesion sites in the gut, produce antimicrobial substances, strengthen the intestinal barrier function, and modulate immune responses. By maintaining a healthy balance of gut bacteria, probiotics may help support digestive comfort. It's important to note that effects are strain-specific and product-dependent.

Whilst probiotics are generally considered safe for most pregnant women, individual responses may vary. It's worth noting that UK antenatal care guidelines do not routinely recommend probiotic supplementation during pregnancy, and their use should be discussed with healthcare professionals on a case-by-case basis.

Benefits of Probiotics for Pregnant Women

Research into probiotic supplementation during pregnancy has identified several potential benefits for maternal health, though the strength of evidence varies across different outcomes. One of the most commonly reported benefits relates to digestive health. Pregnancy-related constipation affects up to 40% of expectant mothers, and certain probiotic strains may help improve bowel regularity and reduce abdominal discomfort, though evidence is limited and variable.

Gestational diabetes mellitus (GDM) prevention represents another area of interest. Some studies suggest that probiotic supplementation may help improve glucose metabolism in pregnant women. However, NICE guidance (NG3) does not recommend probiotics as an intervention for GDM prevention, and lifestyle measures remain the primary focus for managing blood glucose during pregnancy.

Regarding vaginal health during pregnancy, while lactobacilli are the predominant bacteria in a healthy vaginal microbiome, the evidence for probiotic supplementation to prevent or treat bacterial vaginosis during pregnancy is inconclusive. NHS and NICE guidance do not currently recommend probiotics for this purpose, and there is insufficient evidence to suggest they reduce the risk of preterm birth.

Emerging evidence suggests potential benefits for maternal mental wellbeing through the gut-brain axis, though this research is still developing. Some studies indicate that maternal probiotic use might reduce the risk of eczema in infants, but evidence remains mixed, and there is no official UK recommendation for routine use for this purpose. Pregnant women should discuss potential benefits with their midwife or GP, as individual circumstances vary and not all claimed benefits are supported by robust clinical evidence.

Safety and Recommended Probiotic Strains in Pregnancy

Probiotics are generally regarded as safe for healthy pregnant women when used appropriately. The strains most commonly studied in pregnancy have a long history of safe consumption in fermented foods and have been researched in clinical trials. However, as with any supplement during pregnancy, it is advisable to consult with a healthcare professional before commencing probiotic supplementation.

Commonly studied strains with safety data in pregnant populations include:

• Lactobacillus rhamnosus GG – extensively researched for digestive health and studied in relation to infant immune development

• Lactobacillus reuteri – investigated for maternal digestive health (note that evidence for infant colic prevention primarily relates to direct infant supplementation, not maternal use)

• Bifidobacterium lactis (also known as B. animalis subsp. lactis) – studied for digestive comfort

• Lactobacillus acidophilus – commonly used in studies of gut health

• Lactobacillus plantarum – researched for metabolic health

When selecting a probiotic supplement, pregnant women should look for products that clearly identify the bacterial strains and colony-forming units (CFUs). Efficacy is strain- and product-specific, so it's best to follow the manufacturer's instructions for the specific product rather than assuming a standard dose across all probiotics. Products should be manufactured to high quality standards and stored appropriately, as some require refrigeration.

Safety considerations are particularly important for women with compromised immune systems, those with central venous catheters, or those with a history of endocarditis or severe valvular heart disease, as there have been rare reports of probiotic-related infections in vulnerable individuals. Women with these conditions should seek specialist advice. Additionally, check labels for potential allergens (e.g., milk or soy proteins) and avoid products containing additional herbal ingredients that may not be safe during pregnancy.

In the UK, most probiotic supplements are regulated as foods by the Food Standards Agency and local authorities, not by the MHRA (unless they make medicinal claims).

When to Take Probiotics During Pregnancy

The optimal timing for probiotic supplementation during pregnancy depends on the intended health outcome and individual circumstances. There is no universally prescribed schedule, and current evidence does not definitively establish a single 'best' time to begin or continue probiotic use during pregnancy.

Many studies investigating probiotics for metabolic health have initiated supplementation during the first or early second trimester, typically before 16–20 weeks of gestation. However, it is important to note that lifestyle interventions, including diet and physical activity, remain the cornerstone of gestational diabetes prevention according to NICE guidance (NG3), and probiotics should not replace these measures.

For digestive symptoms such as constipation or bloating, probiotics can be started when symptoms arise, at any stage of pregnancy. These supplements may be used on an ongoing basis or intermittently, depending on symptom patterns and individual response. Probiotics should not replace standard NHS-recommended interventions for constipation, such as increased fibre, fluid intake, and safe laxatives when needed.

Research examining infant outcomes, such as eczema prevention, has typically involved maternal supplementation during the third trimester and continuation during breastfeeding. However, the evidence for allergy prevention remains mixed, and there is no official UK recommendation for routine probiotic use for this purpose.

Practical considerations include taking probiotics at a consistent time each day to establish a routine. Some suggest taking probiotics with food may improve tolerability. If you are prescribed antibiotics during pregnancy, separate probiotic doses by at least 2 hours to maintain probiotic viability. Women should follow product-specific guidance for duration of use. If specific pregnancy complications arise, such as threatened preterm labour or other medical concerns, women should consult their obstetrician or midwife before continuing or initiating probiotic supplementation.

Potential Side Effects and Precautions for Expectant Mothers

Whilst probiotics are generally well-tolerated by pregnant women, some individuals may experience mild side effects, particularly when first beginning supplementation. Understanding these potential effects and knowing when to seek medical advice is important for safe use during pregnancy.

Common side effects are typically mild and transient, resolving within a few days as the body adjusts to the probiotic supplement. These may include:

• Digestive discomfort – bloating, gas, or mild abdominal cramping, particularly in the first few days of use

• Changes in bowel habits – temporary alterations in stool frequency or consistency

• Mild nausea – though this can be difficult to distinguish from pregnancy-related nausea

To minimise these effects, pregnant women can start with a lower dose and gradually increase to the recommended amount over several days. Taking probiotics with food may also improve tolerability.

Precautions and contraindications are important to consider. Women with the following conditions should consult a specialist before using probiotics:

• Immunocompromised states or conditions requiring immunosuppressive medication

• History of endocarditis or severe valvular heart disease

• Central venous catheters or other indwelling medical devices

• Short bowel syndrome or intestinal damage

• Severe acute pancreatitis

When to contact your GP or midwife: Pregnant women should seek medical advice if they experience severe abdominal pain, persistent vomiting, fever, or signs of allergic reaction (rash, difficulty breathing, facial swelling) after taking probiotics. Additionally, if there are concerns about any pregnancy complications or if symptoms worsen rather than improve with probiotic use, professional guidance should be sought promptly.

It is essential to inform healthcare providers about all supplements being taken, including probiotics. Check product labels for potential allergens such as milk or soy proteins. If taking antibiotics, separate probiotic doses by at least 2 hours. If you suspect a side effect related to a probiotic supplement, you can report it through the MHRA Yellow Card scheme (website or app).

Frequently Asked Questions