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Are probiotics safe for use during pregnancy and lactation?

Jackie Elias, RPh, Pina Bozzo and Adrienne Einarson, RN

March 2011



There has been a great deal of discussion in both the medical and lay literature about the use of probiotics to improve general health. Subsequently, pregnant women have been asking me if probiotics used for treating conditions such as bacterial vaginosis and diarrhea are safe to use during pregnancy and lactation.


Current data suggest that probiotic supplementation is rarely systemically absorbed when used by healthy individuals. One meta-analysis and several randomized controlled trials conducted with women during the third trimester of pregnancy did not report an increase in adverse fetal outcomes. There have been no published studies addressing Saccharomyces species use in pregnancy. Probiotics are unlikely to be transferred into breast milk.


On a beaucoup parlé, dans les ouvrages médicaux et les médias populaires, de l’utilisation des probiotiques pour améliorer l’état de santé général. Depuis, des femmes enceintes me demandent si les probiotiques utilisés pour traiter des problèmes comme la vaginose bactérienne et la diarrhée sont sécuritaires durant la grossesse et l’allaitement.


Selon les données actuelles, les suppléments de probiotiques sont rarement absorbés systémiquement quand ils sont utilisés par des personnes en santé. Une méta-analyse et quelques études randomisées contrôlées réalisées auprès de femmes durant le troisième trimestre de la grossesse n’ont pas relevé d’augmentation de résultats indésirables pour le fœtus. Aucune étude portant sur l’utilisation des suppléments de Saccharomyces durant la grossesse n’a encore été publiée. Il est peu probable que les probiotiques passent dans le lait maternel.

Probiotics are live microorganisms (in most cases bacteria) that are similar to beneficial microorganisms found naturally in the human gut. They are available to consumers mainly in the form of dietary supplements and foods, and "when administered in adequate amounts confer a health benefit on the host." 1 The most widely used probiotics in Canada are live bacteria such as Lactobacillus and Bifidobacterium species and nonpathogenic yeast such as Saccharomyces. They are available alone or in combination as tablets, drops, liquids, and oral or vaginal capsules; they are also contained in various fermented foods, most commonly yogurt. Probiotics have been used for the treatment of acute diarrhea, antibiotic-associated diarrhea, Clostridium difficile, and yeast and bacterial vaginosis. In healthy humans, lactobacilli are normally present in the oral cavity, ileum, colon, and vagina.

Product safety

When ingested orally or used vaginally, probiotics are generally considered safe and are well tolerated. One theoretical concern associated with probiotics is the potential for these organisms to cause systemic infections. Although rare, probiotic-related bacteremia and fungemia have been reported. 2 It is estimated that the risk of developing bacteremia from ingested Lactobacillus probiotics is less than 1 per 1 million users, 3 and the risk of developing fungemia from Saccharomyces boulardii is estimated at 1 per 5.6 million users, and is estimated to be lower in healthy individuals. 4 There have been no reports of bifidobacterium sepsis associated with the use of probiotics in healthy individuals. 5 Risk factors for systemic infections include immunosuppression, critical illness, central venous catheters, and impairment of the intestinal epithelial barrier. 3 Probiotics administered orally to combat urogenital infections are not systemically absorbed but rather get to the site of action by passage through the gastrointestinal system and ascending into the vagina. 6

Use in pregnancy

Because the risk of probiotic-induced bacteremia and fungemia is low, probiotics are unlikely to reach the systemic circulation of the fetus, and therefore are unlikely to cause harm. A meta-analysis and systematic review of 8 randomized control trials of probiotic use in more than 1500 pregnant women was published. 7 Most of the women began probiotic treatment between 32 and 36 weeks’ gestation and continued until delivery. The studies included in the meta-analysis compared Lactobacillus spp alone or in combination with Bifidobacterium spp with placebo. There was no increase in the incidence of miscarriages or malformations, which was expected because probiotic use mostly occurred in the third trimester and was therefore unlikely to affect organogenesis. There was no significant difference in birth weight, gestational age, or the incidence of cesarean section.

Several randomized control trials conducted in pregnant women in the third trimester of pregnancy were published following the meta-analysis ( Table 1). 815 These studies examined Lactobacillus spp and Bifidobacterium spp as monotherapy or in combination. Although not designed to directly evaluate pregnancy outcomes, these studies did not suggest an increase in adverse outcomes related to probiotics. Two observational studies examining the use of lactobacilli in the first trimester of pregnancy reported no increased risk of malformations. 16, 17

Table 1. Randomized placebo-control trials of probiotics exposure during pregnancy


No. of patients

Period of exposure


Pregnancy outcomes


Boyle et al,8 2008


36 weeks’ gestation to delivery

Lactobacillus rhamnosus GG

Not reported


Kopp et al,9 2008


4–6 weeks before expected delivery to 6 months after delivery

L rhamnosus GG

No significant difference in gestational age, birth weight, or method of delivery

Selected women with uneventful pregnancies and without underlying chronic disease (ie, diabetes mellitus, rheumatoid arthritis, chronic infectious disease)

Kukkonen et al,10 2008


4 weeks before expected delivery

L rhamnosus GG and LC705; Bifidobacterium breve Bb99; and Propionibacterium freudenreichii ssp shermanii JS

No significant difference in birth weight, birth length, and incidence of vaginal delivery

Excluded birth at < 37 weeks’ gestation and infants born with major malformations. Babies also received treatment for 6 months after delivery

Huurre et al,11 2008


First trimester to end of exclusive breastfeeding

L rhamnosus GG and Bifidobacterium lactis Bb12

No significant difference in gestational age or incidence of cesarean section

Women with chronic or metabolic disease before or during early pregnancy were excluded

Kuitunen et al,12 2009


36 weeks’ gestation to delivery

L rhamnosus LC705, B breve Bb99, and P freudenreichii ssp shermanii JS

No significant difference in birth weight

Babies received treatment for 6 months after delivery

Niers et al,13 2009


6 weeks before expected delivery to delivery

Bifidobacterium bifidum W23 and B lactis W52

No significant difference in the incidence of cesarean section, birth weight, or prematurity or gestational age

Babies received treatment for 12 months after delivery

Allen et al,14 2010


36 weeks’ gestation to delivery

Lactobacillus salivarius CUL61 and Lactobacillus paracasei CUL08

No significant difference in adverse events related to pregnancy or childbirth

Babies received treatment for 6 months after delivery

Luoto et al,15 2010,


First trimester to end of exclusive breastfeeding

L rhamnosus GG and B lactis Bb12

No significant differences in incidence of adverse outcomes; significantly lower birth weight (P = .035) and shorter birth length(P = .028)


There are 2 published randomized control trials 11, 15 of women exposed to probiotics commencing in the first trimester until the end of exclusive breastfeeding ( Table 1). 815 Both studies examined the combination of Lactobacillus rhamnosus strain GG and Bifidobacterium lactis compared with placebo. Neither study was specifically designed to examine pregnancy outcomes; therefore, malformations were not reported. Luoto et al 15 found that infants born to women in the probiotics group had statistically significant lower risk of increased birth weight (P = .035) and birth length (P = .028); however, the clinical significance of this slight difference is unknown. This finding was not confirmed in the study by Huurre et al. 11 Both studies demonstrated no significant difference in gestational age or the incidence of cesarean section. There have been no published studies addressing Saccharomyces spp as an intervention for pregnant women.

Use in breastfeeding

Because probiotics are rarely systemically absorbed, they are not expected to transfer into breast milk. One randomized control trial examined Lactobacillus reuteri levels in 174 colostrum samples after maternal and infant oral supplementation of this probiotic. 18 Although higher in the active than in the placebo group, the prevalence of L reuteri in colostrum was low and not clinically important. Abrahamsson et al 18 suggested that the most likely origin of L reuteri in colostrum was external contamination from the gastrointestinal tract. There are no published data regarding adverse effects in breastfed infants. In several of the studies previously mentioned, 10, 1214 infants received probiotic therapy after delivery without an increase in adverse effects.


Probiotics do not appear to pose any safety concerns for pregnant and lactating women. Systemic absorption is rare when probiotics are used by healthy individuals, and the current literature does not indicate an increase in adverse pregnancy outcomes.

Motherisk questions are prepared by the Motherisk Team at The Hospital for Sick Children in Toronto, Ont. Ms. Elias is a doctoral candidate in the Faculty of Pharmacy at the University of Toronto. At the time this paper was written, Ms. Bozzo was a member and Ms. Einarson was Assistant Director of the Motherisk Program. Ms. Bozzo is now Assissant Director and Ms. Einarson continues to be a member of the Motherisk Program.

Do you have questions about the effects of drugs, chemicals, radiation, or infections in women who are pregnant or breastfeeding? We invite you to submit them to the Motherisk Program by fax at 416 813-7562; they will be addressed in future Motherisk Updates.

Published Motherisk Updates are also available on the Canadian Family Physician website ( www.cfp.ca).

View abstract

Competing interests
None declared

Canadian Family Physician
March 2011 vol. 57 no. 3 299-301
Copyright © 2011 by The College of Family Physicians of Canada


  1. Food and Agriculture Organization of the United Nations, World Health Organization. Guidelines for the evaluation of probiotics in food. London, ON: Food and Agriculture Organization of the United Nations and World Health Organization; 2002. Available from: www.who.int/foodsafety/fs_management/en/probiotic_guidelines.pdf. Accessed 2010 Oct 28.
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