Probiotic Lactobacillus rhamnosus species: considerations for female reproduction and offspring health

Abstract

Lactobacillus rhamnosus is a type of bacteria known as a probiotic and is often used to support the health of the digestive system and vaginal flora. This type of bacteria has an important role, showing positive effects on female reproductive biology, particularly by maintaining the balance of microorganisms in the vagina, reducing the risk of infection, and strengthening the immune system to support maternal health during pregnancy. There are also studies showing that these probiotics prevent maternal obesity and gestational diabetes. Consuming probiotics containing Lactobacillus rhamnosus strains may support the intestinal health of breastfeeding mothers, but they may also contribute to the health of offspring. Therefore, this review focuses on the current available data for examining the effects of Lactobacillus rhamnosus strains on female reproductive biology and offspring health. A systematic search was conducted in the PubMed and Web of Science databases from inception to May 2024. The search strategy was performed using keywords and MeSH (Medical Subject Headings) terms. Inconsistent ratings were resolved through discussion. This review is strengthened by multiple aspects of the methodological approach. The systematic search strategy, conducted by two independent reviewers, enabled the identification and evaluation of all relevant literature. Although there is a limited number of studies with high heterogeneity, current literature highlights the important contribution of Lactobacillus rhamnosus probiotics in enhancing female reproductive health and fertility. Furthermore, the probiotic bacteria in breast milk may also support the intestinal health of newborn, strengthen the immune system, and protect them against diseases at later ages.

Introduction

The study of microorganisms involved in female reproduction offers potential opportunities for the development of important therapeutics, including probiotics. A growing number of studies show that animal systems have extensive microbiomes that contribute to the health of the host and normal physiology [1, 2]. The human microbiota plays an important role in the protection of not only women’s health but also men’s and newborn health [3]. The male reproductive microbiota is mainly found in semen, while the female microbiota is found all over the female reproductive system [4, 5]. In this context, Lactobacillusrhamnosus species are among the strains that have been studied the most in terms of female health. These strains are important microorganisms that control much of the reproductive microbiome and act by preventing pathogens from entering the reproductive tract [6]. Therefore, we reviewed the impact of Lactobacillus rhamnosus strains on female reproductive biology and offspring health. We further discuss the potential benefits of probiotic therapies to improve reproductive function and the children’s health born to probiotic-treated mothers.

Effects of probiotic Lactobacillus rhamnosus strains on female reproductive health

Synergistic relationships between microorganisms and hosts are found in almost every niche of the human body regulating physiology and pathophysiology [7]. The female genital tract, vagina, cervix, endometrium, fallopian tubes, and ovaries contain their own microbiome, which makes up 9% of the total amount of bacteria in the female body [8]. While the majority of Lactobacillus species make up the healthy vagina, there are fewer and very variable amounts of bacterial strains in the upper genital tract [9]. Among the factors involved in the development of microbiota are the mode of delivery, mother’s microbiota, breast milk intake, environmental exposure to bacteria, use of antibiotics, probiotics, and nutrition.

The presence of Lactobacillus is directly related to vaginal pH < 4.5, which is known to produce abundant lactic acid. Lactic acid–induced acidity has been strongly associated with protection against cervicovaginal infections, including HIV and other sexually transmitted infections [10, 11]. Lactobacillus rhamnosus BPL005 was found to have protective roles on endometrial infections by lowering pH and producing organic acids in vitro [12]. Beyond lactic acid, Lactobacillus strains are associated with beneficial properties such as production of bacteriocins (antimicrobial peptides), attachment to the vaginal epithelium, and the ability to use available nutrients competitively [13, 14]. Lactobacillus strains are also associated with estrogen production in the core of the dominant vaginal microbiota and accumulation of glycogen in the upper layers of the stratified vaginal epithelium [15, 16]. It has also been reported that a probiotic combination containing Lactobacillus rhamnosus LRH020 prevents menopause-related symptoms [17].

Current literature indicates that probiotic and symbiotic supplementation may improve polycystic ovary syndrome (PCOS)–related changes in inflammatory markers, lipid metabolism, and hormonal profiles [2, 18, 19]. Despite the complexity and incomplete elucidation of PCOS’s pathophysiology, a connection between obesity, PCOS, and dysbiosis has been noted [20–24]. A clinical study by Kaur and colleagues showed that multispecies probiotics, along with dietary and lifestyle changes, significantly improved testosterone and insulin levels, LH/FSH ratio, insulin resistance, menstrual cycle regularity, and ultrasonography screening [25]. Nutritional interventions are necessary in the treatment of PCOS because obesity has been reported to worsen all symptoms of PCOS (especially insulin resistance (IR) and hyperandrogenism) [26, 27]. In contrast, the study by Lagowska and Kapczuk revealed that probiotic supplementation and nutritional intervention containing 12 × 10⁹ CFU/ml Lactobacillus rhamnosus GG (LGG) had no beneficial effect on anthropometric parameters, carbohydrate metabolism, or androgen status in overweight and obese women [28]. Although the vaginal and intestinal microbiome compositions in PCOS have been investigated, the studies in the literature are insufficient and the mechanism is not fully known. The studies relevant to the effects of Lactobacillus rhamnosus strains important for female reproductive health are summarized in Table 1.

Table 1.

Summary of main studies mentioned in this review for the effects of probiotic Lactobacillus rhamnosus strains on female reproductive health

Test group	Probiotic species	Duration	Results	References
Women aged 18–40 diagnosed with PCOS (n = 104)	Lactobacillus acidophilus UBLA-34 (2.0 billion), Lactobacillus rhamnosus UBLR-58 (2.0 billion), Lactobacillus reuteri UBLRu-87 (2.0 billion), Lactobacillus plantarum UBLP-40 (1.0 billion), Lactobacillus casei UBLC-42 (1.0 billion), Lactobacillus fermentum UBLF-31 (1.0 billion), Bifidobacterium bifidum UBBB-55 (1.0 billion)	2 capsules per day for the first 2 months, 2 capsules per day for the next 4 months	Improved testosterone and insulin levels, LH/FSH ratio, insulin resistance, body weight, BMI, menstrual cycle irregularity	[25]
Overweight and obese women with PCOS (n = 40)	Lactobacillus rhamnosus GG (12 × 109 CFU/ml)	20 weeks	No additional beneficial effects on intestinal bacterial abundance, anthropometric parameters, carbohydrate metabolism, SCFA levels, or lipid profile	[28]
Cell-free supernatant of Lactobacillus rhamnosus	Lactobacillus rhamnosus RD-0060	Incubation for 17–24 h	Good therapeutic effect on BV by inhibiting Gardnerella vaginalis	[29]
Women 26–30 weeks pregnant with and without BV (n = 140)	Lactobacillus rhamnosus GR-1 and Lactobacillus Reuteri RC-14 (1 × 109 CFU/ml)	30 days	A decrease in Gardnerella vaginalis and an increase in Prevotella copri	[30]
Women with a gestational age of less than 12 weeks (n = 10)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (1 × 109 CFU/ml)	8 weeks	No impact on vaginal health	[31]
Healthy pregnant women aged 18 to 55 years and less than 36 weeks gestation (n = 38)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (1 × 109 CFU/ml)	30 days	Association with healthy vagina and birthing with high bacterial diversity	[32]
Women over 18 years of age with risk factors for premature birth and normal vaginal flora (Nugent score ≤ 3) (n = 40)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (5 × 109 CFU/ml)	2 months	Decreased rate of vaginal Lactobacillus colonization	[33]
Women over 16 years of age and 9–14 weeks pregnant (n = 238)	Lactobacillus rhamnosus GR-1 and Lactobacillus Reuteri RC-14 (2.5 × 109 CFU/ml)	1 capsule until birth	No change on the vaginal microbiota and no prevention of BV	[34]
Women aged 18–45 with signs and symptoms of vaginal dysbiosis (n = 72)	Lactobacillus rhamnosus CA15 (DSM 33960) (1 × 1010 CFU/ml)	10 days	Normalization of physiological pH, increased lactobacilli rate with reduction of pathogens, and improvement of normal vaginal microbiota	[35]
Women aged 18–40 diagnosed with an adverse vaginal microbiota and undergoing fertility treatment (n = 74)	Lactobacillus gasseri EB01 (DSM14869) (> 1 × 108 CFU/ml) and Lactobacillus rhamnosus PB01 (DSM14870) (> 1 × 108 CFU/ml)	10 days	No effects on normal vaginal flora	[36]
Cell-free supernatant probiotics	Lactobacillus acidophilus ATCC 314, Lactobacillus plantarum DSM 17938, Lactobacillus rhamnosus ATCC 7469, and Lactobacillus reuteri ATCC 8014	48 h	Reduced Candida parapsilosis, increased epithelial resistance, and prevention in the onset of mucosal Candida parapsilosis infection	[37]
Women aged 23–61 years (n = 60)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (2.5 × 1010 CFU/ml)	2 months	Increased Lactobacillus strains in fecal samples, unchanged Lactobacillus strain quantity in vaginal or oral sites	[38]
Women aged 18–45 years and less than 25 weeks gestation (n = 139)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (2.5 × 1010 CFU/ml)	2 capsules per day for 12 weeks	Similar vaginal/rectal GBS colonization rates between probiotic and non-probiotic groups	[39]
Lactobacillus rhamnosus L60 and Lactobacillus fermentum supernatants	Bacteriocin-like substances (BLIS) produced by Lactobacillus rhamnosus L60 and Lactobacillus fermentum (1.5 × 108 CFU/ml)	24 h	BLISs produced by Lactobacillus fermentum L23 and Lactobacillus rhamnosus L60 reduced the growth of Streptococcus agalactiae	[40]
Women 35–37 weeks pregnant with a positive diagnosis of GBS (n = 110)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (1 × 109 CFU/ml)	2 capsules per day until birth	Reduced vaginal and rectal GBS colonization in pregnant women	[41]

Vaginal infections

The vaginal genital tract is populated by many microbial species, primarily Lactobacillus species, that live in balance as a balanced microbiota responsible for the healthy condition of the vagina and maintaining an acidic pH (pH < 4.5) [42, 43]. A healthy urogenital system plays an important role in protecting against vaginal infections, and vaginal Lactobacillus are important because of their protective functions such as adhesion to vaginal tissue and production of antimicrobial agents [44]. Unfortunately, pathogenic bacteria (e.g., Streptococcus agalactiae, Escherichia coli, Gardnerella vaginalis) can migrate from the gastrointestinal tract to the lower urogenital tract [45]. Thus, it can cause diseases such as urinary tract infections, bacterial vaginosis (BV), aerobic vaginitis (AV), and vulvovaginal candidiasis (VVC) [46].

BV is a common vaginal disease associated with abnormal changes in the vaginal microbiome [47]. It is the most common cause of vaginal infection among childbearing women, and its prevalence varies between 4.9 and 36.0% according to European and American studies [48, 49]. Generally, Lactobacillus and other microorganisms appear together in the vagina to maintain the microecological balance [50]. Some obstetrical and gynecological adverse outcomes such as miscarriage, preterm delivery, and upper reproductive tract infections may also be associated with BV [51]. In a clinical study recently conducted by Huang and colleagues, the growth inhibition mechanism of cell-free supernatant of Lactobacillus rhamnosus RD0060 against Gardnerellavaginalis, which has a therapeutic effect on BV, revealed that the probiotic produced high levels of lactic acid and acetic acid to inhibit the growth of Gardnerella vaginalis [29]. Thus, the overgrowth of Gardnerella vaginalis is important during BV, but the possible cause of BV is due to excessive alteration of the vaginal microbiome [29]. In another study, the treatment with Lactobacillusrhamnosus GR-1 and Lactobacillusreuteri RC-14 for 30 days (1 × 10⁹ CFU/ml) also reduced Gardnerella vaginalis [30]. In contrast, there are other reports stating that the same probiotic administrations for 8 weeks had no effect on vaginal health [31]. The small number of cases used in this study may have resulted in the insufficient effect of probiotic supplementation. Thereafter, other administration routes could be more effective in supporting the vaginal microbiota.

The different doses of supplementation of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 were also demonstrated to be effective in preventing bacterial growth and therefore can be used in the treatment and prevention of BV [32–34]. In a study investigating the effects of capsules containing Lactobacillusacidophilus GLA-14 and Lactobacillusrhamnosus HN001 (5 × 10⁹ CFU/ml) on the degree of vaginal colonization, the short-term effect of these probiotics significantly increased the vaginal levels [46]. Thereafter, it was emphasized that supplementation of Lactobacillus rhamnosus CA15 (1 × 10¹⁰ CFU/ml) [35], Lactobacillus gasseri EB01 DSM14869 (> 1 × 10⁸ CFU/ml), and Lactobacillus rhamnosus PB01 DSM14870 (> 1 × 10⁸ CFU/ml) [36] strains for 10 days improved the quality of life in women with vaginal dysbiosis. Considering these studies, the different doses of Lactobacillus rhamnosus strains, especially GR1, HN001, CA05, and PB01 strains, are the most researched and effective probiotics in preventing BV on vaginal health.

Another vaginal infection is VVC, a common clinical condition with signs and symptoms of vaginal inflammation in the presence of Candida species [37]. Seventy-five percent of women of reproductive age experience at least one episode of VVC in their lifetime [52]. Studies suggest that Lactobacillus species such as Lactobacillus acidophilus ATCC 314, Lactobacillus plantarum DSM 17938, Lactobacillus rhamnosus ATCC 7469, and Lactobacillus reuteri ATCC 8014 may play a role in preventing the onset of mucosal Candida parapsilosis infection in the context of the vaginal microbiota [37]. Interestingly, the presence of Lactobacillus rhamnosus strain was only 1.1% in specimens from fertile women. On the other hand, the results regarding human cervical swab microbiota have been found to be associated with ART outcomes. Statistically significant differences were found in the levels of Lactobacillus salivarius and Lactobacillus rhamnosus species [53]. Moreover, the abundance of these bacteria identified is not only useful as an indicator of adverse pregnancy outcomes but may also pave the way for new interventional strategies based on manipulation of the genital tract microbiota to increase pregnancy rates in women. Chen and colleagues also showed that the long-term consumption of probiotics (2.5 × 10¹⁰ CFU/ml) of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 on the cervicovaginal microbiome is beneficial in the treatment of women with VVC and may offer a safe and effective option for the prevention of recurrent infections in women [38].

Chlamydia trachomatis is another pathogen that infects the urogenital system and can cause hydrosalpinx and tubal fibrosis. Chlamydia muridarum infection is a well-known model for studying human Chlamydia pathogenicity in the genitourinary tract [54]. However, there are very limited data available to date regarding the mechanism of action of LGG on upper reproductive tract infection. Based on our current knowledge, only one study showed that oral LGG administration had no effect on preventing this infection with LGG (5 × 10⁸ CFU/ml) supplementation for 19 days [55].

Group B streptococci (GBS) are types of bacteria that colonize the vagina in pregnant women and can therefore cause serious infections in newborn who pass through the birth canal [56]. Vaginal or rectal colonization of GBS during pregnancy has been associated with early-onset GBS disease, which is one of the leading causes of neonatal morbidity and mortality [57]. The vaginal/rectal colonization rate of GBS was evaluated in participants between 35 and 37 weeks of gestation in Canada. Two capsules of probiotics (2.5 × 1010 CFU/ml Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri) were given to a group with 113 individuals for 12 weeks [39]. The results showed that the rates of vaginal/rectal GBS colonization were similar between groups given and not given probiotics [39]. Even though this preliminary study can serve as the basis for a larger, suitably powered study, the main limitation was including all participants in the intervention regardless of their GBS status at enrollment. Ruiz and colleagues investigated the inhibitory activities of the bacteriocin-like inhibitory substance (BLIS) produced by (1.5 × 10⁸ CFU/ml) Lactobacillusrhamnosus L60 and Lactobacillusfermentum L23 and the effects of combined BLIS of these lactobacilli on GBS. The study reported that BLISs produced by these lactobacilli of vaginal origin can inhibit Streptococcus agalactiae isolates; thus, these strains may have probiotic potential for GBS control in females and consequently prevent GBS infections in newborn [40]. Similarly, it was shown that GBS colonization results changed from positive to negative, and (1 × 10⁹ CFU/ml) Lactobacillusrhamnosus GR-1 and (1 × 10⁹ CFU/ml) Lactobacillusreuteri RC-14 probiotic administration could reduce the rate of vaginal and rectal GBS colonization in pregnant women [41]. The results of these two studies support the idea that increasing the amount of Lactobacillus can reduce GBS colonization. However, it is a major deficiency that the actual mechanism has not yet been investigated. Within the scope of this information, more research on the vaginal and endometrial microbiomes is definitely required.

Effect of probiotic Lactobacillus rhamnosus species during pregnancy: potential therapeutic options for maternal obesity and gestational diabetes

It has been widely demonstrated that dysbiotic or pathological modifications of this microbial profile can cause gynecological disorders, preterm delivery, pregnancy complications such as preeclampsia, and reproductive failure [11, 58–60]. During pregnancy and/or lactation, the balance of the female reproductive microbiome can be altered through various external parameters such as vaginal infection, antibiotic therapy, obesity status, and GDM, which in turn has an impact on both long-term host-microbe relationships and human development [61]. Currently, the use of various probiotic strains such as Bifidobacterium, Lactobacillus, and Saccharomyces is potentially easy, accessible, and safe to reduce the development of cervicovaginal microbiome dysbiosis during pregnancy as well as to support IVF performance [62].

Maternal obesity and GDM are associated with various health problems for mother and child during pregnancy, childbirth, and later life [63, 64]. Overweight and obese women tend to gain more weight than recommended during pregnancy, which is also linked to adverse pregnancy outcomes [65–68]. In a randomized study conducted by Pellonpera and colleagues, the effects of fish oil and probiotics on GDM risk and maternal glucose concentrations were examined. The study revealed that probiotic capsules containing Lactobacillus rhamnosus HN001 and Bifidobacterium animalislactis (1 × 10¹⁰ CFU/ml) taken as supplements throughout pregnancy did not affect the development of GDM [69]. However, reduced adiposity has also been found in women with GDM compared to normoglycemic women, regardless of dietary intervention [69]. In contrast to this study, a new study has shown that a combination of fish oil and probiotics containing Lactobacillus rhamnosus HN001 and Bifidobacteriumanimalis lactis (1 × 10¹⁰ CFU/ml) may affect serum fatty acid levels in pregnant women with obesity [70]. Similar to the study of Pellonpera and colleagues, the beneficial effect of capsules containing the same dosage and the same probiotics on vaginal microbiota composition from early to late pregnancy was found to be associated with a reduced abundance of potential pathobionts such as Peptoniphilus, Dialister, and Campylobacter [71]. This is actually a very important result since pregnancy itself predisposes women to vaginal dysbiosis, and therefore, probiotic consumption can prevent pregnant women from developing the condition and adverse pregnancy outcomes such as preterm delivery.

In another study evaluating the safety and efficacy of probiotics containing LGG and Bifidobacterium lactis BB12 on maternal and infant outcomes in the treatment of women with GDM, the investigators stated with low-certainty evidence that there was not any difference between probiotics and placebo in postpartum hemorrhage, gestational age, fasting plasma glucose, preterm birth, macrosomia, birth weight, head circumference, height, infant hypoglycemia, and neonatal intensive care unit admissions [72]. However, the effectiveness of the information to guide practice is hampered by the heterogeneity of the probiotics utilized and the small sample sizes of the trials. On the other hand, Wickens and colleagues also reported that probiotic Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) supplementation at 14–16 weeks of pregnancy was found to be successful in preventing GDM in pregnant women [73]. As supported by different studies, pregnancy in women can trigger the development of overweight and obesity, which is associated with the risk of disease, and probiotic application can prevent this situation.

It was reported that dietary counseling and probiotic supplementation (LGG and Bifidobacterium lactis 1 × 10¹⁰ CFU/ml) for 12 months in normoglycemic pregnant women had better glucose tolerance in this group compared to the control/placebo group and that probiotic administration had a curative effect [74]. Therefore, balanced glucose metabolism maintained with these probiotics during pregnancy may provide long-term health effects on the mother and future child. Otherwise, in a study conducted by Nachum and colleagues, 2-week probiotic combination containing Lactobacillus rhamnosus (6 × 10⁹ CFU/ml) did not affect the glycemic parameters of the mother in pregnant women with GDM [75]. It has also been shown that Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) supplementation during pregnancy reduces conjugated bile acids, which may play a role in improving glucose metabolism, has no significant effect on fasting lipids, and has weaker bile acid lowering effects [76]. In contrast, a study by Callaway and colleagues reported that probiotics administered from the second trimester of pregnancy did not prevent GDM in overweight and obese pregnant women, nor did they improve the secondary conditions such as neonatal complications and maternal blood pressure [77]. However, OGTT was not applied to each participant before the experiments, and the participants initially comprised the trial population, which may not clearly reflect the findings.

Dietary and physical activity interventions during pregnancy can reduce maternal gestational excess weight gain and further improve maternal and infant outcomes [78, 79]. In a different study in a multiethnic New Zealand population, dietary education and/or different doses of probiotic capsules (6.5 × 10⁹/7 × 10⁹ CFU/ml LGG and Bifidobacterium lactis BB-12) did not alter excess pregnancy weight gain and birth weight ratios [80]. Jaakkola and colleagues studied the participants who consumed LGG and Bifidobacterium lactis Bb12 probiotic supplements (1 × 10¹⁰ CFU/ml) from the first trimester of pregnancy until the end of exclusive breastfeeding and up to 6 months after birth [81]. Thereafter, even 4 years after birth, the risk of both overweight and central adiposity was lower in women taking probiotics compared to those not taking supplements [81]. It is also known that probiotic supplemented dietary counseling containing LGG and Bifidobacteriumlactis (1 × 10¹⁰ CFU/ml) in the first trimester of pregnancy is effective in controlling maternal weight as well as body composition during and after pregnancy [82]. Thus, the impact of probiotic-assisted dietary counseling on central adiposity may offer a new avenue for obesity prevention and management. A summary of the studies for the effects of Lactobacillus rhamnosus species during pregnancy and lactation periods is presented in Table 2.

Table 2.

Summary of main studies mentioned in this review for the effects of probiotic Lactobacillus rhamnosus strains during pregnancy and lactation periods

Test group	Probiotic species	Duration	Results	References
Pregnant overweight or obese women (n = 439)	Lactobacillus rhamnosus HN001 (1 × 1010 CFU/ml) and Bifidobacterium animalis ssp. lactis 420 (1 × 1010 CFU/ml) with or without fish oil	Throughout pregnancy	Not effective in the development of GDM, reduced vaginal pathobionts	[69, 71]
Overweight and obese pregnant women (n = 439)	Lactobacillus rhamnosus HN001 (1 × 1010 CFU/ml) and Bifidobacterium animalis ssp. lactis 420 (1 × 1010 CFU/ml) with or without fish oil	From early pregnancy to the 6th month after birth	Increased serum n-3 LC-PUFA levels	[70]
Women in 14–16 weeks of pregnancy (n = 348)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml)	From 14–16 weeks of pregnancy to birth	Not effective in postnatal maternal or infant anthropometric measurements, but successful in preventing GDM	[73, 76]
Normoglycemic pregnant women (n = 256)	Lactobacillus rhamnosus GG and Bifidobacterium lactis (1 × 1010 CFU/ml) in combination with dietary counseling	12 months	Better glucose tolerance	[74]
Pregnant women (n = 85)	Probiotic combination containing strains of Bifidobacterium bifidum, Bifidobacterium lactis, Lactobacillus acidophilus, Lactobacillus paracasei, Lactobacillus rhamnosus, and Streptococcus thermophilus (6 × 109 CFU/ml)	2 weeks	Did not effect the glycemic index	[75]
Overweight and obese pregnant women (n = 411)	Lactobacillus rhamnosus GG and Bifidobacterium animalis lactis (1 × 1010 CFU/ml)	From the 2nd trimester of pregnancy to the 28th week	Did not prevent GDM or improve secondary conditions such as neonatal complications and maternal blood pressure	[77]
Pregnant women with a body mass index of ≥ 30 kg/m2 at 12–17 weeks (n = 230)	Lactobacillus rhamnosus GG and Bifidobacterium lactis (6.5 × 109 CFU/ml)	Throughout pregnancy	No change on excess weight gain during pregnancy and birth weight rates	[80]
Pregnant women in the first trimester of pregnancy (n = 256)	Lactobacillus rhamnosus GG and Bifidobacterium lactis (1 × 1010 CFU/ml) with dietary consultancy	From the first trimester of pregnancy until 6 months after delivery	Lower risk of overweight and central adiposity even 4 years after giving birth	[81, 82]
Pregnant women between 10 and 16 weeks with a Nugent score of 4 and a moderate vaginal microbiota with or without Lactobacilli (n = 129)	Vaginal tablets containing Lactobacillus casei rhamnosus (> 1 × 107 CFU/ml)	8 days	A tendency to have beneficial effects during pregnancy	[83]
Pregnant women with a Nugent score > 3 at 8–20 weeks (n = 4204)	Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (2.5 × 109 CFU/ml)	12 weeks	Did not cause adverse pregnancy outcomes	[84]
Pregnant women (n = 43) and their neonates (n = 29)	Lactobacillus rhamnosus GG and Bifidobacterium lactis (1 × 109 CFU/ml)	From late pregnancy to birth	Significantly modulated the expression of TLR-related genes in both the placenta and fetal intestine	[85]
Human placental trophoblast cells	Lactobacillus rhamnosus GR-1	12 h after the beginning of cell starvation for a duration of 12 h	Induced phosphorylation of STAT3-Tyr705, providing a potential protection against infection and inflammation-mediated PTB	[86]
Pregnant women with PROM at 24–36 weeks of gestation (n = 27)	Vaginal tablets containing Lactobacillus rhamnosus and Lactobacillus gasseri (1 × 109 CFU/ml)	10 days	Increased delay in labor in women with PROM	[87]
Preterm women with PPROM and 23–31 weeks of pregnancy (n = 40)	Ampicillin and Lactobacillus casei rhamnosus (> 40,000 CFU/ml) treatment	Until birth	Extended latent period in patients with PPROM far from term	[88]
Women during pregnancy and lactation and their infants (n = 96)	Lactobacillus rhamnosus GG (1 × 1010 CFU/ml)	4 weeks before birth, 6 months after birth	Positive effects on the maturation process of the infant’s intestinal immunity	[89]
Pregnant and lactating mothers (n = 71) and their neonates	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml) and Bifidobacterium lactis (9 × 109 CFU/ml)	2–5 weeks before birth and 6 months after birth, 2 months for infants	Effective on fetal immune parameters during lactation, but not effective on TGF-β/IgA profiles	[90]
Pregnant and lactating mothers (n = 423) and their neonates	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml) and Bifidobacterium lactis (9 × 109 CFU/ml)	Only for the mother from 14–16 weeks of pregnancy until the 6th month after birth	Not effective on TGF-β/IgA profiles	[91]
Pregnant mothers (n = 423) and their infants	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml)	14–16 weeks during pregnancy and during lactation for 6 months after birth	Decrease in eczema and atopic sensitivity, especially in infants between 6 and 12 months	[92]
Women aged 18–40 with 12–24 weeks pregnant (n = 56)	Probiotic yoghurt containing Lactobacillus rhamnosus GR-1 enriched withMoringa plant (1 × 1010 CFU/ml)	During pregnancy and for 1 month after birth	Increased Bifidobacterium abundance, decreased Enterobacteriaceae in neonatal feces but no impact on the microbiota of mother	[93]
Pregnant mothers (n = 1223) and their 3-month-old infants (n = 428)	Multistrain probiotic containing Bifidobacterium breve Bb99 (2 × 108 CFU/ml), Propionibacterium freudenreichii shermanii JS (2 × 109 CFU/ml), Lactobacillus rhamnosus Lc705 (5 × 109 CFU/ml), and Lactobacillus rhamnosus GG (5 × 109 CFU/ml)	Supplement for mothers from the 35th week until birth and 6 months after birth for infants	Supported microbiota in infants born by cesarean section and treated with antibiotics	[94]

Preterm birth (PTB)

Despite progress in perinatology, prevention of PTB is still a leading issue in obstetrics [95]. The healthy vaginal microbiota, dominated by Lactobacillus rhamnosus species, is an important protective factor against vaginal infections potentially associated with PTB [96]. PTB occurs in 9 to 13% of all human pregnancies and accounts for 80% of all neonatal morbidity and mortality [97]. In a retrospective study, Petricevic and colleagues found that the absence of vaginal Lactobacillus in the first trimester of pregnancy in pregnant women who used vaginal tablets containing Lactobacillus caseirhamnosus (> 1 × 10⁷ CFU/ml) for 8 days may increase the risk of PTB in women with moderate microbiota. It is also emphasized that in addition to BV and infection, it is important to address the absence of vaginal Lactobacillus during pregnancy [83]. It was reported that probiotic administration of Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri RC-14 (2.5 × 10⁹ CFU/ml) for 12 weeks during pregnancy did not cause adverse consequences during pregnancy in women with low risk of PTB in accordance with other studies [84, 98]. Therefore, its use was suggested to be safe and vaginal microbiota showed flux despite this oral probiotic administration [99].

About 40% of all PTBs are idiopathic, and about half are associated with infection or an active inflammatory process. In this context, Koscik and colleagues investigated the ability of the probiotic Lactobacillus rhamnosus GR-I to modulate cytokine and chemokine production from amniotic cells in response to stimulation by lipopolysaccharide (LPS) and lipoteichoic acid [60] [100]. The probiotic administration reduced the effect of both LPS and LTA in stimulating the proinflammatory cytokine TNF-α. Thus, it was speculated that Lactobacillus rhamnosus GR-1 has ability to stimulate immune cells to a level where they can protect against infections while at the same time reducing the accompanying proinflammatory response. However, to assess the significance of this link in human pregnancy or early miscarriage, more research is needed. Similarly, probiotic supplementation given to the mother in late pregnancy significantly modulates the expression of TLR-related genes in both the placenta and fetal gut. This study also suggested that microbial contact in utero is associated with changes in the innate immune gene expression profiles and that fetal and placental immune physiology may be modulated by specific probiotics [85].

Lactobacillus rhamnosus GR-1 was also found to induce phosphorylation of STAT3-Tyr705 in human placental trophoblast cell cultures. Therefore, the data provides a fundamental intracellular mechanism for Lactobacillus rhamnosus GR-1–mediated cytokine modulation in the human placenta and possible protection against infection- and inflammation-mediated PTB [86]. Accordingly, the administration of Lactobacillus rhamnosus can enhance the beneficial effects and offer a real alternative for the prevention and treatment of inflammatory processes such as those that occur in premature birth. The probiotic Lactobacillusrhamnosus GR-1 (2 × 10⁷–10⁸ CFU/ml) supernatant has been shown to reduce the LPS-induced inflammation and PTB in vivo in pregnant CD-1 mice providing therapeutic benefits in preventing infection-induced PTB by controlling systemic and intrauterine inflammation [101].

Premature rupture of membranes (PROM) affects 8–10% of all pregnancies and contributes to 20–40% of preterm births that may occur at term (> 37 weeks of gestation) or preterm (< 37 weeks of gestation) [102]. Restoring the balance of the vaginal microbiota and strengthening the natural immunity seem to be very important to achieve better pregnancy outcomes, especially in women with PROM. Probiotic vaginal tablets containing Lactobacillus rhamnosus and Lactobacillus gasseri (1 × 10⁹ CFU/ml) administered for 10 days prolonged the latent and gestation periods in women with PROM (< 37 gestational weeks) [87]. It also seems like ampicillin plus Lactobacillus caseirhamnosus (> 40,000 CFU/ml) treatment reduces the laboratory indicators of infection and the frequency of harmful maternal and neonatal events in preterm PROM cases [88]. However, most of these studies are retrospective with small number of patients. Therefore, before suggesting this as a therapeutic modality in PTB, there is no doubt that multicenter, prospective, and randomized controlled trials are required.

Maternal microbiome during the lactation periods

The milk and mammary gland microbiome can be affected by a variety of factors, including mode of delivery, breastfeeding, maternal lifestyle, health status, and diet [103–105]. An increasing number of studies show various positive effects of probiotic consumption during lactation on mother and newborn [106].

Breast milk is a well-characterized source of immunologically active compounds, namely, immunoglobulins, cytokines, oligosaccharides, long-chain polyunsaturated fatty acids, maternal immune cells, and living microbes [107]. Liu and colleagues isolated and identified lactic acid bacteria (LAB) from human colostrum [108]. Based on morphology and 16S rRNA sequence, a total of 197 LAB strains were identified from human colostrum, including eight Bifidobacterium strains and 10 Lactobacillus strains [108]. The study group screened two strains, Bifidobacterium lactis Probio-M8 and Lactobacillus rhamnosus Probio-M9, with probiotic potential [108]. These two strains may make it easier to conduct functional research on the probiotics found in breast milk and to create probiotics obtained from human milk.

Several studies have indicated the direct influence of consumed probiotics on milk microbiota. Rinne and colleagues administrated a probiotic supplement containing LGG (1 × 10¹⁰ CFU/ml) to mothers for 4 weeks before delivery and 6 months after delivery [89] reporting that the total number of IgG-secreting cells in breastfed infants given probiotic supplementation was higher than in the control group, and this was correlated with the concentration of sCD14, IgM, IgA in colostrum [89]. Therefore, it can be suggested that probiotics may positively affect intestinal immunity during breastfeeding. Prescott and colleagues reported that probiotic supplementation containing Lactobacillusrhamnosus HN001 (6 × 10⁹ CFU/ml) and Bifidobacteriumlactis HN019 (9 × 10⁹ CFU/ml) during 2–5 weeks of pregnancy before birth and 6 months postpartum has the potential to affect fetal immune parameters as well as immunomodulatory factors in breast milk [90]. Therefore, probiotic supplements taken during breastfeeding might also positively affect intestinal immunity. However, Wickens and colleagues showed that Lactobacillusrhamnosus HN001 could not be detected in breast milk and TGF-β/IgA profiles were not changed from probiotic (6 × 10⁹ CFU/ml)-supplemented mothers [91]. The abundance of bacteria in breast milk may have been affected since the mothers participating used perinatal antibiotics, and the probiotic HN001 was very sensitive.

In a clinical trial, the probiotic effects of yoghurt and raw milk were compared from mothers who received probiotic supplementation (Lactobacillus rhamnosus HN001, 6 × 10⁹ CFU/ml) for 6 months during breastfeeding [92]. The results revealed that yoghurt might be a safe alternative to raw milk and yoghurt could be introduced to infants as early as 6 months for possibly early protection against sensitization [92]. In line with this study, consumption of probiotic yoghurt containing Lactobacillusrhamnosus GR-1 enriched with Moringa plant (1 × 10¹⁰ CFU/ml) had no effect on microbiota in any part of the mother’s body, but a significant increase in vaginal microbiota diversity up to and after delivery was detected [93]. Since there was an increased relative abundance of Bifidobacterium and decreased Enterobacteriaceae in the newborn feces, further investigation is needed given the infants’ gut microbial profile improved as a result. On the other hand, infants born through cesarean section or given antibiotics are more likely to have metabolic, inflammatory, and immunological problems, possibly because of disruption of normal gut microbiota during a critical developmental time window.

Using a combination of taxonomic, metagenomic, and metaproteomic approaches, Korpela and colleagues showed that probiotic supplementation containing Bifidobacterium breve Bb99 (2 × 10⁸ CFU/ml), Propionibacterium freudenreichii shermanii JS (2 × 10⁹ CFU/ml), Lactobacillusrhamnosus Lc705 (5 × 10⁹ CFU/ml), and LGG (5 × 10⁹ CFU/ml) to both mothers and breastfed infants might correct undesirable changes in microbiota composition caused by antibiotic treatments or cesarean section [94]. In fact, optimal duration of probiotic supplementation to prevent microbiota disturbance still needs to be investigated. From another point of view, it seems like different probiotic bacteria may have a different ability to transfer from the mother to the child [109].

The role of maternal microbiomes in the offspring

The developing immune system of the fetus is markedly shaped by the intrauterine environment. The microbiota can be transmitted from mother to children in a variety of ways, including feces, vaginal delivery, skin, and breastfeeding. Therefore, maternal gut microbiota has a significant influence on the microbial composition of the offspring [110]. The overall implications of the effects of maternal microbiome on the offspring metabolism, immune system, allergic diseases, and perinatal psychological disorders are summarized in Table 3.

Table 3.

Summary of main studies mentioned in this review for the effects of maternal microbiomes on the offspring metabolism, immune system, allergic diseases, and perinatal psychological disorders

Test group	Probiotic species	Duration	Result	References
Pregnant women in the first 3 months of pregnancy (n = 256) and their 6-month-old infants (n = 194)	Lactobacillus rhamnosus GG and Bifidiobacterium bifidum (1 × 1010 CFU/ml)	From early pregnancy to the end of the lactation period	Reduced risk of high split proinsulin and leptin/adiponectin ratio in breastfed infants	[111]
Pregnant women (n = 159) and their infants (n = 113)	Lactobacillus rhamnosus GG (1 × 106 CFU/ml)	Supplements for 4 weeks before birth and 6 months postpartum. If mothers were not lactating, infants were treated for 6 months	Effective in the first stage of overweight gain in overweight children but not in the second stage	[112]
Pregnant women in the first 3 months of pregnancy and their neonates (n = 256)	Lactobacillus rhamnosus GG and Bifidiobacterium lactis Bb12 (1 × 1010 CFU/ml)	From the first 3 months of pregnancy to the end of lactation	Reduced the incidence of GDM, showed no adverse effects on mothers or neonates	[113]
Pregnant women 30–36 weeks and their neonates (n = 88)	Lactobacillus rhamnosus GG (2 × 109 CFU/ml)	From 30 to 36 weeks of pregnancy until birth	Presence of LGG colonization in neonates and its stabilization for 6 months	[114, 115]
Pregnant women in the 3rd trimester of pregnancy and their infants (n = 80)	Lactobacillus rhamnosus and Bifidobacterium longum (2 × 109 CFU/ml) and Lactobacillus paracasei + Bifidobacterium bifidum (2 × 109 CFU/ml) combinations	For 2 months before birth and 2 months after birth	No effects on intestinal colonization frequencies of infants aged 1–6 months and a little effect on the mother-baby relationship	[116]
Pregnant women in the 2rd trimester of pregnancy (n = 60) and school children (n = 44)	Yogurt containing Lactobacillus rhamnosus GR1 (1 × 1010 CFU/ml)	From 12 to 24 weeks of pregnancy until the end of birth, 25 days for children	Protective effects on the pregnant women’s blood levels of mercury and arsenic from additional increases, however no tendency for the offspring	[117]
Primary trophoblast cells purified from normal human term placentas (n = 6)	Heat killed Lactobacillus rhamnosus GG (1 × 1010 CFU/ml)	Incubation of syncytiotrophoblast cells for 3 h at 37 °C at doses of 0, 106, 108, and 1010 CFU/ml	Reversed LPS-induced TNF-α release and stimulated IL-4 and IL-10 expressions	[118]
Pregnant women and their infants (n = 331)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml) and Bifidobacterium lactis HN019 (9 × 109 CFU/ml)	From the 35th week of pregnancy until the end of lactation; from birth until the age of 2 for infants	Significant reduction in the development of eczema and atopic sensitization until at least 11 years of age	[119, 120]
Pregnant women in their 35th week of pregnancy and their infants (n = 82)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml)	Throughout pregnancy and until the infants are 7 months old	Association of the release of IL-10 from cord blood mononuclear cells with the incidence of AD in infants with fecal Bifidobacterium	[121]
Pregnant women in their 36th week of pregnancy (n = 415)	Probiotic capsules containing combinations of Lactobacillus rhamnosus GG (5 × 1010 CFU/ml), Bifidobacterium animalis lactis Bb-12 (5 × 1010 CFU/ml), and Lactobacillus acidophilus La-5 (5 × 109 CFU/ml)	From the 36th week of pregnancy to the 3rd month after birth	Preventive effect on AD partially by reducing the Th22 cell rate in 3-month-old infants	[122]
Pregnant women in their 35th week of pregnancy and their infants (n = 425)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml) and Bifidobacterium animalis lactis HN019 (9 × 109 CFU/ml)	Supplementation for mothers from the 35th week of pregnancy to the 6th month after birth and up to 2 years of age for infants	Protective effect against eczema in children up to at least 4 years of age	[123]
Pregnant women in the 2rd trimester of pregnancy and their infants (n = 205)	Combination containing Lactobacillus rhamnosus LPR and Bifidobacterium longum BL999 (LPR + BL999 (1 × 109 CFU/ml)), Lactobacillus paracasei ST11, and Bifidobacterium longum BL999 (ST11 + BL999) (1 × 109 CFU/ml)	Last 2 months of pregnancy and first 2 months of lactation	Reducing the risk of eczema in children with allergic mothers	[124]
Pregnant women in their 36th week of pregnancy and their infants (n = 73)	Lactobacillus rhamnosus GG (1.8 × 1010 CFU/ml)	From the 36th week of pregnancy until birth	Modulation of fetal immune responses may not be a major mechanism that LGG prevent eczema	[125]
Pregnant women in their 36th week of pregnancy (n = 250) and their infants (n = 98)	Lactobacillus rhamnosus GG (1.8 × 1010 CFU/ml)	From the 36th week of pregnancy until birth	Ineffective in regulating the diversity of early infant gut microbiota	[126]
Pregnant women in their 35th week of pregnancy (n = 1223) and infants at high risk of allergies (n = 925)	Combination of 4 probiotic strains containing Lactobacillus rhamnosus GG (5 × 109 CFU/ml), Lactobacillus rhamnosus LC705 (5 × 109 CFU/ml), Bifidobacterium breve Bb99 (2 × 108 CFU/ml), and Propionibacterium freudenreichii shermanii JS (2 × 109 CFU/ml) with galactooligosaccharides	Pregnant women 2–4 weeks before and until birth, infants for 6 months after birth	No effects on the incidence of all allergic diseases by age 2 years but prevention of eczema and particularly atopic eczema	[127, 128]
Pregnant women with BMI ≥ 30.0 (n = 230)	Lactobacillus rhamnosus GG (6.5 × 109 CFU/ml) and Bifidobacterium lactis Bb12 (6.5 × 109 CFU/ml)	12–17 weeks of pregnancy week to 36th week	Not effective in improving mental health	[129]
Pregnant women 14–16 weeks (n = 423)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml)	Throughout pregnancy and lactation	Reduced anxiety and depression in postpartum mothers	[130]
Pregnant women in their 35th week of pregnancy and their infants (n = 342)	Lactobacillus rhamnosus HN001 (6 × 109 CFU/ml) and Bifidobacterium animalis lactis HN019 (9 × 109 CFU/ml)	From the 35th week of pregnancy to the 6th month after birth and from birth to 2 years of age for infants	No association with neurocognitive outcomes at 11 years of age	[131]
Pregnant women and their infants (n = 132)	Lactobacillus rhamnosus GG (1 × 1010 CFU/ml)	For 6 months postpartum	Did not interfere with the normal growth of the infant and the gut microbiota’s compositional development	[132]
Healthy women and men between the ages of 18–50 (n = 70)	Limosilactobacillus fermentum LF16, Lacticaseibacillus rhamnosus LR06, Lactiplantibacillus plantarum LP01, and Bifidobacterium longum 04 probiotic combination (4 × 109 CFU/ml)	Supplementation for 2, 4, and 6 weeks	Improved sleep quality	[133]

Effects of maternal microbiomes on the offspring’s metabolism

High pre-pregnancy body mass index and excessive weight gain during pregnancy are associated with abnormalities in the mother’s gut microbiota composition [134]. This acts as a vaccine for the development of the infant gut microbiota and thus has the potential to interfere with the healthy colonization of the infant gut [135].

The maternal diet can be readjusted during pregnancy and lactation periods potentially with benefits on the metabolic health of the children. It has been shown that positive metabolic programming, especially measured by a lower high proinsulin ratio, can be achieved by balancing the mother’s diet with Lactobacillus rhamnosusGG and Bifidobacterium lactis (1 × 10¹⁰ CFU/ml) probiotics and breastfeeding the infant during pregnancy [111]. In another study, Luoto and colleagues administered probiotic supplements containing Lactobacillus rhamnosus GG (1 × 10¹⁰ CFU/ml) to pregnant women 4 weeks before birth, and anthropometric measurements of the children were taken at 3, 6, 12, and 24 months and at 4, 7, and 10 years of age. The results showed that perinatal probiotic intervention alleviated the initial phase of excessive weight gain in initiating during fetal period, but did not moderate the second phase of excessive weight gain starting after the age of 24–48 months, the impact being most pronounced at the age of 4 years old [112]. It was also reported that perinatal Lactobacillus rhamnosus GG and Bifidobacterium lactis (1 × 10¹⁰ CFU/ml) probiotic supplementation reduced the incidence of GDM, resulting in a normal pregnancy period without any negative effects on mothers or children [113].

Effects of maternal microbiomes on the offspring’s immune system

The prenatal period is a sensitive period when intrauterine exposures can alter the course of development and have a lasting impact on the offspring, leading to lifelong changes in the fetal immune system [136]. Establishment of the gut microbiota at birth provides an important source of microbial stimuli for the maturation of the immune system. However, deviations in this process precede the development of certain diseases and provide the rationale for using probiotics to counter them [137].

Schultz and colleagues studied whether the administration of probiotics containing Lactobacillus rhamnosus GG (2 × 10⁹ CFU/ml) to pregnant women at 30–6 weeks causes colonization in the infant. The results revealed that temporary colonization of an infant with Lactobacillus rhamnosus GG is possible by colonizing the pregnant woman before birth. It was also reported that this colonization is stable for only 6 months but may continue for up to 24 months in unexplained cases [114]. The study of Bisanz and colleagues showed that consumption of probiotic yoghurt containing Lactobacillus rhamnosus GR-1 (1 × 10¹⁰ CFU/ml) had a protective effect against high mercury and arsenic levels in pregnant women, but this trend was not statistically significant. The high blood lead in children was also associated with increased relative abundance levels of Succinivibrionaceae and Gammaproteobacteria in feces [117]. In a similar study by Nallagatla and colleagues, the supplementation of a synbiotic formulated with prebiotic and probiotic Lactobacillus rhamnosus GG (2 × 10⁹ CFU/ml) to pregnant mothers was effective in improving cellular and humoral immunity [138]. It is also known that heat-killed Lactobacillus rhamnosus GG (1 × 10¹⁰ CFU/ml) probiotic supplementation reverses LPS-induced TNF-α release from trophoblast cells and stimulates IL-4 and IL-10 expressions [118].

Studies conducted on experimental animals within the scope of this subject have shown that probiotics supplemented to mothers in the early period positively modulate the health of the offspring. It has been shown that Lactobacillus rhamnosus GG (1 × 10⁸ CFU/ml) probiotic supplementation given to mothers before birth significantly supports intestinal development, inhibits low-grade intestinal inflammation, and changes the intestinal microbiota composition of weaned puppies. It has also been reported that Lactobacillus rhamnosus GG colonization at an early age reduces the diversity of intestinal tumors in adulthood through inhibition of Wnt signaling [139].

It was reported that Lactobacillus rhamnosus GG colonization was detected in the feces of 3-week-old puppies after Lactobacillus rhamnosus GG (1 × 10⁷ CFU/ml) probiotic supplement to mothers from the 18th day after pregnancy until birth and between 0 and 5 days after birth, and the beneficial effects of early Lactobacillus rhamnosus GG colonization on the microbiota continued for up to 8 months. The abundance of bacteria associated with longevity (Lactobacillus, Bifidobacterium, and Akkermansia) was increased significantly in the Lactobacillus rhamnosus GG colonization group, and Lactobacillus rhamnosus GG colonization protected the intestinal barrier, increased antioxidant defense, reduced epithelial cell DNA damage, and prevented low-grade intestinal inflammation [140]. The live and inactive Lactobacillus rhamnosus GG probiotic administration to pregnant mice until birth (1 × 10⁸ CFU/ml) and to pups until the fifth day after birth (1 × 10⁷ CFU/ml) significantly increased the intestinal epithelial cell proliferation, differentiation, tight junction formation, and mucosal IgA production in Lactobacillus rhamnosus GG-colonized mice [141].

Bifidobacterium breve was found higher and Bifidobacterium adolescent strain was lower in neonates whose mothers took Lactobacillus rhamnosus GG probiotic supplements for 4 weeks before birth and until the end of birth. Therefore, Lactobacillus rhamnosus GG consumption seems to increase bifidobacterial diversity in neonates and reduce the similarity of Bifidobacterium microbiota between mother and infant [115]. In contrast, it has been shown that the combination of probiotics (Lactobacillus rhamnosus, Bifidobacterium longum, Lactobacillus paracasei, and Bifidobacterium bifidum) given to the mother 2 months before birth and 2 months after birth almost does not affect the intestinal colonization of infant aged 1–6 months and has little effect on the mother-infant relationship [116]. Therefore, these studies report a significant correlation in the intestinal microbiota between mothers and infants and the existence of specific strains that can modulate the colonization process more significantly than others, especially in newborn.

The antibiotic-induced decrease in intestinal microbiota diversity also affects immune cell development [142]. In a related study, administration of the probiotic Lactobacillus rhamnosus HN001 (1 × 10¹⁰ CFU/ml) to newborn pups from 1 week before birth to 1 week after birth was shown to regulate granulopoiesis and most T cell activation in neonatal mice suffering from antibiotic-induced disrupted gut microbiota. In addition, administration of probiotics to pups during the first week of life revealed the immune-homeostatic beneficial effect of the probiotic in all cell populations examined in the bone marrow and spleen [143]. Intrahepatic cholestasis of pregnancy is a pregnancy liver disease characterized by increased bile acid levels in maternal serum [144]. Studies have shown that cholestatic pregnancy can cause long-term metabolic disorders in offspring [145, 146]. In a study conducted in this context, it was found that supplementing Lactobacillus rhamnosus LRX01 (2 × 10⁸ CFU/ml) to pups during the first two days after birth inhibited farnesoid X receptor (FXR) expression in the ileum of the pups and could improve intestinal immunity [147].

Effects of maternal microbiomes on the offspring’s allergic disease

Atopic dermatitis (AD), also known as eczema, is a chronic inflammatory skin disease that has recently been recognized as the leading cause or precursor of other atopic conditions such as food allergy and asthma [148, 149]. It is estimated that 30% of infants are diagnosed with AD based on the ratio of drugs prescribed. Lactobacillus rhamnosus strains are the most extensively studied strain to date in the treatment of AD, and their potential to prevent AD has also been explored. Studies in the literature show that the use of Lactobacillus rhamnosus alone or in combination with other probiotics during and after pregnancy in infants has a positive effect on reducing the incidence of AD [150].

In this line, there are several studies evaluating the effectiveness of probiotics in preventing the development of pediatric AD. In the study of Wickens and colleagues, the cumulative effects of Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) and Bifidobacterium lactis HN019 (9 × 10⁹ CFU/ml) probiotics were evaluated in children up to 11 years of age showing that HN001, in particular, could provide protection against the development of eczema and atopic sensitivity until at least 11 years of age [119]. The study’s 11-year data collecting follow-up was truly remarkable, but the study was limited by declining participation rates and response bias over such a long period of time. In a cohort study, pregnant participants were given probiotic supplements containing heat-killed Lactobacillus rhamnosus GG and Bifidobacterium bifidum until their infants were 7 months old. It was thought that impairment of IL-10 production in response to microbial stimuli at birth may be associated with an increased risk of infantile Alzheimer’s disease [121]. Therefore, altered immune responses and intestinal colonization of beneficial bacteria early in life may contribute to AD prevention. In a study by Ro and colleagues, participants were supplemented with probiotic capsules containing combinations of Lactobacillus rhamnosus GG (5 × 10¹⁰ CFU/ml), Bifidobacterium animalislactis Bb-12 (5 × 10¹⁰ CFU/ml), and Lactobacillus acidophilus La-5 (5 × 10⁹ CFU/ml) from the 36th week of pregnancy until the third month after birth. The probiotic combination applied reduced the Th22 cell rate in 3-month-old children and partially demonstrated the protective role of probiotics on Alzheimer’s disease [122].

There is strong evidence to support a genetic predisposition to eczema, and more recent studies have suggested that probiotics can be used to prevent eczema by altering the expression of genes putatively associated with allergy [120, 151]. In a study with a high-risk infant population, participants were given a daily supplement of Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) and Bifidobacterium animalislactis HN019 (9 × 10⁹ CFU/ml) probiotics from the 35th week of gestation until birth, until the sixth month postpartum in breastfeeding mothers, and from birth to 2 years of age in all children [120]. The study results revealed that 26 TLR SNP interacted with HN001 to significantly reduce the risk of eczema compared to placebo, with HN001 showing a much stronger effect than HN019 in this regard [120]. A very similar study also reported that the same dose of strain HN019 did not affect the prevalence of any eczema-related outcomes, but the protective effect of HN001 against eczema was reported to persist until at least 4 years of age when given only in the first 2 years of life [123]. In fact, this probiotic may be a suitable preventive intervention for high-risk infants. Since the immune modulating effects of bacteria can be strain-specific, it is not surprising that the HN001 probiotic is found to be more effective, and the accuracy of the high 4-year response rate is the strength of these studies. The probiotic combination supplement containing Lactobacillus rhamnosus LPR and Bifidobacterium longum BL999 (LPR + BL999), Lactobacillus paracasei ST11, and Bifidobacterium longum BL999 (ST11 + BL999) (1 × 10⁹ CFU/ml) given to the mother during pregnancy and breastfeeding significantly reduced the risk of eczema development in high-risk infants [124]. Although the main mechanism that prevents eczema is unknown, possibly Lactobacillus rhamnosus GG (1.8 × 10¹⁰ CFU/ml) treatment could not be the main mechanism that prevents eczema [125]. Additionally, it was shown that Lactobacillus rhamnosus GG (1.8 × 10¹⁰ CFU/ml) probiotic application could not modulate the diversity of the intestinal microbiota of infants at high risk of allergic diseases [126]. In a large cohort of allergy-prone infants, it was reported that the combination of four probiotic strains containing Lactobacillus rhamnosus GG (5 × 10⁹ CFU/ml), Lactobacillus rhamnosus LC705 (5 × 10⁹ CFU/ml), Bifidobacterium breve Bb99 (2 × 10⁸ CFU/ml), and Propionibacterium freudenreichii shermanii JS (2 × 10⁹ CFU/ml) with galactooligosaccharides given to newborn infants 2 to 4 weeks before birth and for 6 months after birth had no effect on the incidence of all allergic diseases until 2 years of age, but significantly prevented atopic eczema [127]. However, the same group reported that these probiotics increased the resistance to respiratory tract infections in the first 2 years of life after the treatment with the same strain was given to their infants for 6 months [128].

The microbiome in mother-infant interaction and perinatal psychological disorders

The perinatal period, which includes pregnancy, childbirth, and the postpartum period, is inherently stressful [152]. Negative early life experiences can affect brain development and be associated with developing psychopathological disorders, including stress, anxiety, and depression [153]. It has been demonstrated that gut dysbiosis is involved in bidirectional interactions in the gut-brain axis and participates in the progression of multiple disorders such as anxiety [154]. It is known that obesity during pregnancy increases the risk of poor maternal mental health and related physical and mental health complications [155]. Poor maternal mental health has been associated with numerous pregnancy and child health complications [156]. In a clinical study conducted by Dawe and colleagues, it was reported that administration of probiotics containing Lactobacillus rhamnosus GG and Bifidobacterium lactis BB12 (6.5 × 10⁹ CFU/ml) until the 36th week of pregnancy did not improve mental health outcomes in a group of pregnant women with obesity [129]. Apart from the limited antenatal follow-up in this study, another drawback is the absence of an objective way to quantify capsule consumption. In contrast, Slykerman and colleagues showed that Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) given during pregnancy and postnatal period lowered depression and anxiety in postnatal mothers [130]. The same research team also evaluated the effect of Lactobacillus rhamnosus HN001 (6 × 10⁹ CFU/ml) and Bifidobacterium animalislactis (9 × 10⁹ CFU/ml) probiotics on 11-year-old children and found that these probiotics administered from the 35th week of pregnancy to the sixth month after birth and 2 years of age did not make a difference in the neurocognitive outcomes of children [131]. Rinne and colleagues also reported that probiotic containing Lactobacillus rhamnosus GG (1 × 10¹⁰ CFU/ml) administered for 6 months after birth did not make any difference on similar processes such as vomiting and crying times in infants [132]. Additionally, a new study reported that a combination of probiotics, including the Lactobacillus rhamnosus LR06 strain (4 × 10⁹ CFU/ml), improved sleep disturbances in women [133]. Within the scope of this subject, the studies are insufficient, and it can be suggested that probiotic applications containing Lactobacillus rhamnosus strains may be potentially useful in the prevention or treatment of postnatal depression and anxiety symptoms, but more studies are needed.

Conclusions

Studies based on the available evidence highlight the important contribution of probiotics in enhancing body health in general and in enhancing fertility in women in particular. Lactobacillus strains are among the most commonly used species to modulate reproductive system abnormalities (Fig. 1). The biological activities of Lactobacillus rhamnosus strains (including antioxidant, antimicrobial, anti-inflammatory, and immunomodulatory activities) offer promising opportunities to restore reproductive dysbiosis and improve reproductive performance and fertility traits. This review evaluated the available evidence regarding the effects of probiotic interventions with Lactobacillus rhamnosus strains on the reproductive health of females and their offspring. However, the main limitation of this review is the lack of homogeneity across studies regarding the health status of the participants, the composition and duration of the dietary supplement administered, and the method used to measure the outcomes assessed. Currently, the proposed mechanisms by which probiotics benefit reproduction include modulation of microbiota composition, regulation of metabolism, promotion of the epithelial barrier, and improvement of immune function. Probiotic treatments, including Lactobacillus rhamnosus strains, seem to be an effective way to improve reproductive health in females and their offspring. These studies in humans or animal models indicate that Lactobacillus rhamnosus strains are suitable candidates for probiotic sources to maintain and restore reproductive eubiosis.

Fig. 1.

Effects of probiotic Lactobacillus rhamnosus species treatment on female and offspring health. There are two different ways to administer probiotic Lactobacillus rhamnosus species: oral and intravaginal. A Oral administration. Probiotic Lactobacillus rhamnosus species taken orally must travel via the mouth, stomach, intestines, and colon before reaching the vagina via skin contact in the perineum. B Intravaginal administration. Probiotic Lactobacillus rhamnosus spp can also be administered intravaginally using external devices. C Lactobacillus rhamnosus probiotics may improve metabolic regulation and positively affect reproductive outcomes by altering the microbiota composition and enhancing the immune response. At the same time, the absence of these bacteria can trigger diseases such as PCOS, BV, AV, VVC, and GDM. D The use of maternal probiotic Lactobacillus rhamnosus species during pregnancy contributes to the oral, placental, gut, and vaginal microbiomes and increases the dominance of Lactobacillus in these microbiomes. Thus, it can improve glycemic and lipid status during pregnancy, reduce inflammation, prevent oxidative stress, and minimize the risk of GDM, EGWG, obesity, and PTB. Lactobacillus probiotics, which can be transferred to the offspring through the birth method, prevent possible diseases in the future by affecting the development of the newborn’s intestinal microbiome. E In addition to the richness of macro- and micronutrients, breast milk contains many microorganisms such as Lactobacillus strains, some of which are taken from the mother and some from the infant’s mouth and the environment. These microorganisms initiate the development of the gastrointestinal tract microbiota as well as the milk microbiota in infants and contribute to the development of immune regulatory factors. These factors play an important role in reducing the risk of developing chronic diseases such as atopic dermatitis, food allergy, asthma, and psychological disorders later in life (PCOS polycystic ovary syndrome, BV bacterial vaginosis, AV aerobic vaginitis, VVC vulvovaginal candidiasis, GDM gestational diabetes, EGWG excessive gestational weight gain, PTB preterm birth, SCFA short-chain fatty acid)

Abbreviations

LGG

Lactobacillus rhamnosus GG

PCOS

Polycystic ovary syndrome

IR

Insulin resistance

BV

Bacterial vaginosis

AV

Aerobic vaginitis

VVC

Vulvovaginal candidiasis

ART

Assisted reproductive technologies

GBS

Group B streptococci

BLIS

Bacteriocin-like inhibitory substance

GDM

Gestational diabetes

IVF

In vitro fertilization

PTB

Preterm birth

LPS

Lipopolysaccharide

TNF-α

Tumor necrosis factor alfa

TLR

Toll-like receptor

PROM

Premature rupture of membranes

LAB

Lactic acid bacteria

IL

Interleukin

FXR

Farnesoid X receptor

AD

Atopic dermatitis

ELS

Early life stress

MS

Maternal separation

Data availability

Related resources are available at https://pubmed.ncbi.nlm.nih.gov.

Declarations

Conflict of interest

The authors declare no competing interests.