Probiotics are living microorganisms that benefit health. Many of these microorganisms are bacteria, which are often thought of as something we should avoid. While there are “bad” bacteria that can cause illness, probiotics are considered “good” bacteria that are critical for normal digestive functioning. Specifically, they help to break down food and ensure that nutrients are well absorbed.
Probiotic supplementation during pregnancy can offer a number of advantages. To accommodate a growing baby, pregnant women undergo a wide array of physiological changes, including in the types and distributions of microorganisms in their bodies.
Scientists have suggested that altering this gut “microflora” in expecting mothers may prevent complications during pregnancy. For instance, using probiotic supplementation may improve outcomes related to mucosal immunity, urogenital infections and intestinal dysbiosis .
It is not only the mother who is affected by the changes in microflora. Studies have shown that the mother’s gut during the 3rd trimester can influence the immune system and insulin insensitivity in the fetus, both of which have implications for the developing baby’s health .
Studies looking at the impact of probiotic supplementation during pregnancy have shown promising results related to pre-eclampsia  and pre-term delivery , as well as for the likelihood that the child endures gestational diabetes mellitus , abnormal weight gain , or necrotizing enterocolitis .
The relationship between microorganisms and allergic disease in children has been particularly well studied, and there is good reason to believe that probiotics could also alleviate allergies and atopic diseases in infants .
One longitudinal study showed that greater diversity in microflora was associated with lower incidences of eczema in infants and that consumption of probiotic milk during pregnancy reduced the risk of atopic eczema in children at 6 months of age , .
Other studies have demonstrated that administering Lactobacilli, a common bacteria found in milk, during pregnancy reduces the likelihood of atopic eczema in children aged 2 to 7 years .
Are probiotics safe for consumption during pregnancy?
Probiotics are generally regarded as “safe.”. They do not tend to have a significant impact on healthy individuals because they are not usually absorbed in this group of people . Clinical trials conducted during third trimester of pregnancy suggest that there is no increased risk of adverse fetal outcomes associated with probiotic supplements.
The studies also show that there is a low risk of of probiotics being transferred to breast milk . In pregnancy, probiotic consumption is unlikely to negatively impact adverse pregnancy outcomes or cause harm to either lactating mothers or the fetus .
Nevertheless, immunosuppressed patients and patients with leaky gut or significant gastrointestinal disease have an increased risk of sepsis when using probiotics and so must exercise caution .
How do probiotics work?
Though the way that probiotics work is not fully understood, the scientific community generally agrees that probiotics work by crowding out “bad” bacteria with “good bacteria.”
Because “good” bacteria multiple much faster than “bad” bacteria and compete for the same resources, adding “good” bacteria to our microflora can help eliminate “bad” bacterial strains from the digestive tract .
In addition, because many harmful microorganisms do not survive the harsh acidic environment of the stomach, but some probiotic strains can, probiotics that are swallowed can have a positive impact on gut microflora  .
What are the other therapeutic benefits of probiotics?
While probiotics may be specifically beneficial during pregnancy, they have also been shown to have a number of other therapeutic effects [6, 7]., particularly related to digestion.
For instance, research has shown that probiotics can improve outcomes for conditions such as antibiotic-associated diarrhea in adult patients  and irritable bowel disease .
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