Probiotics are generally considered safe to take during pregnancy. Clinical trials involving thousands of pregnant women have found no increase in adverse events compared to placebo, and no harmful effects on newborns. That said, not all probiotics are equal, and the benefits depend on what you’re hoping to achieve.
What the Safety Evidence Shows
The most commonly studied probiotics in pregnancy belong to the Lactobacillus and Bifidobacterium families, which are the same types found in yogurt and most over-the-counter supplements. In one controlled trial of 454 mother-infant pairs, researchers gave women a daily multi-strain probiotic during the last month of pregnancy and continued it for infants through six months of age. Adverse events occurred at nearly identical rates in the probiotic and placebo groups: 6.8% of mothers taking probiotics reported side effects versus 9% in the placebo group. None of the adverse events were attributed to the probiotics themselves.
Across multiple trials, the pattern holds. Probiotics taken orally during pregnancy do not appear to increase the risk of preterm birth, cesarean delivery, or newborn complications. The doses used in these studies typically range from 1 billion to 10 billion colony-forming units (CFU) per day, taken as a single capsule.
Potential Benefits for Blood Sugar
The strongest evidence for probiotics during pregnancy involves gestational diabetes. A meta-analysis pooling data from 10 randomized controlled trials and nearly 3,000 participants found that probiotics reduced the incidence of gestational diabetes by 33%. Multi-strain formulations (those combining several bacterial species) showed the greatest effect. Importantly, the analysis found no significant harms related to probiotic use, including no changes in rates of preeclampsia, excessive weight gain, or newborn complications like low blood sugar or NICU admission.
This doesn’t mean probiotics replace standard blood sugar screening or dietary management. But for women concerned about gestational diabetes risk, especially those with a family history, probiotics may offer a modest protective effect.
Effects on Infant Eczema
Some research suggests that taking probiotics during pregnancy and breastfeeding can lower your baby’s chances of developing eczema in the first two years of life. In one trial, mothers who took probiotic combinations during pregnancy and nursing saw a statistically significant reduction in their infant’s risk of developing eczema compared to those who received a placebo. The effect held for both persistent and short-term eczema.
This is particularly relevant if you or your partner have a history of allergies, asthma, or eczema, since those conditions tend to run in families. The probiotics used in these studies were started during the third trimester and continued through several months of breastfeeding.
Where Probiotics Fall Short
Not every claimed benefit holds up under scrutiny. Two areas where probiotics have been tested in pregnancy with disappointing results are vaginal health and Group B Strep colonization.
In a randomized trial of 40 pregnant women, oral probiotics taken for 60 days during early to mid-pregnancy showed no effect on vaginal flora or bacterial vaginosis markers. The bacteria from oral supplements simply didn’t make it to the vaginal microbiome in meaningful numbers. Only 1 out of 20 women in the probiotic group had detectable Lactobacillus on vaginal swabs afterward. If vaginal health is the goal, oral probiotics likely aren’t the answer.
Similarly, a multicenter trial of 267 pregnant women found that probiotics had no effect on Group B Strep colonization rates or the need for antibiotics during labor. While the probiotics did produce some favorable shifts in vaginal bacteria overall, they didn’t reduce the specific concern most women have about GBS in late pregnancy.
Common Side Effects
The most frequently reported side effects of probiotics, whether you’re pregnant or not, are mild digestive symptoms: gas, bloating, and loose stools. These tend to appear in the first few days as your gut adjusts and usually resolve within a week or two. Starting with a lower dose and increasing gradually can help minimize discomfort.
For healthy pregnant women, serious side effects are essentially absent from the clinical literature. The situation is different for anyone with a severely compromised immune system, where live bacteria supplements carry a theoretical risk of infection. This applies to a very small number of people, such as those on immunosuppressive medications or with certain chronic conditions. If that describes you, it’s worth a conversation with your provider before starting any probiotic.
Choosing a Quality Supplement
Because dietary supplements aren’t regulated as strictly as medications, the label on a probiotic bottle doesn’t always match what’s inside. The only way to verify a product’s contents is through independent lab testing. Look for supplements that carry a third-party certification seal, which confirms that the product contains what it claims in the amounts listed. Recognized seals include USP Verified, NSF Certified, Informed Sport, and BSCG Certified Drug Free. These certifications verify label accuracy and manufacturing quality, though they don’t evaluate whether the product is effective for any specific condition.
When selecting a strain, the research most relevant to pregnancy has used Lactobacillus rhamnosus, Bifidobacterium bifidum, and Bifidobacterium lactis, either alone or in combination. Doses in successful trials typically fall around 5 to 10 billion CFU per day in a single capsule. Multi-strain formulations appear to offer slightly better results for blood sugar regulation than single-strain products.
Probiotic-rich foods like yogurt, kefir, sauerkraut, and kimchi also contribute beneficial bacteria and are safe throughout pregnancy, though they deliver lower and less consistent bacterial counts than supplements.