Probiotics. What are their role in pregnancy and fertility?

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What are probiotics and do they play a role in pregnancy and fertility?

Probiotics are everywhere these days, are they not?  They seem to be a miracle cure for everything under the sun, but what are they really? And what do they actually do?  And should you really care about them when TTC or pregnant?




First, let’s start with the basics.  What exactly are probiotics?  Probiotics are LIVE bacteria (note, sometimes other organisms like yeast qualify as a probiotic too).  But they aren’t just any old bacteria.  They are live bacteria that set up camp in your gut or other areas of your body (like your vagina if you are a woman) and offer a benefit to the host (in this case, YOU!).  Not every bacteria is considered a probiotic.  Some bacteria do not benefit the host, and can actually cause harm to the host. Take E. Coli for example.  If E. Coli sets up camp in your gut, you will likely be living on the potty for quite a while…and not in a good way (is there a good way???).  E. coli is a bacteria, but not a probiotic.  





There are various types of probiotics, and each work in their own way.  Probiotics are a blanket word for the many genus and species of the live bacteria that benefit us humans.  Different probiotics offer different benefits.  Just like a doctor would prescribe a different antibiotic or other drug depending on the condition you may be suffering from, probiotics tackle different conditions as well.  


Probiotics are ingested via food (or supplements) and often survive the digestive process before they reach the gut.  One they reach the gut, they colonize, or make their home.  One important thing people need to realize is that if they are making a point to take in probiotics, they must take them consistently to ensure the colonization is consistent.  Just like drugs are needed to be taken every day to be effective, the same goes for probiotic ingestion.  You cannot take probiotic-rich food one day a week and expect to see results.  


One of the most popular probiotics are those that are from the lactobacillus genus.  Lactobacillus feed off of prebiotics, or undigestible fiber. Just like how we have by-products when we eat some foods (gas!), the lactobacillus have a byproduct called lactic acid.  So, lactobacillus produce lactic acid in the gut. Here is one way that lactobacillus benefits us humans:


The lactic acid that is produced by the lactobacillus is an ACID.  This is important because the production of the acid makes the gut an acidic environment.  Guess who can’t survive in an acidic environment?  Gas-producing and potentially-harmful bacteria and coliforms like E. Coli. So, ingesting lactobacillus, and in turn supporting an acidic environment in your gut, keeps the bad icky guys away.  This is a good idea and a good thing.  


This is just one way that lactobacillus benefits humans.  Other probiotics, like those in the Bifidobacterium genus, have their own mechanism of action as well, and depends on the species too.  




Probiotics are being recommended more frequently during pregnancy, and for good reason.  Some evidence suggests that certain strains may play a role in preeclampsia, gestational diabetes mellitus, vaginal infections, maternal and infant weight gain and allergic diseases (eczema). When the probiotic profile is not ideal during pregnancy, data has shown that the following risk factors were increased:

·     risk of miscarriage

·     premature rupture of membranes 

·     preterm birth.


A very brief list of potential benefits of taking certain probiotic strains consistently and in specific doses is below (this is beyond not an inclusive list of the literature): 


Lactobacillus rhamnosus


Combo of lactobacillus rhamnosus and bifidobacterial longum


Lactobacillus reuteri-containing lozenges

  • May reduce pregnancy gingivitis.

Lactobacillus fermentum

  • May reduce mastitis risk when taken prenatally. 


 Authors of one article did an amazing job summarizing the data, so I will be using their article as a reference for most of my claims below.  


More data regarding fertility and probiotics is coming out, especially since The Human Microbiome Project.  This project showed that the female reproductive tract microbiota accounts for approximately 9% of the total bacterial load in humans. The probiotics are mostly Lactobacilli in healthy women, but other probiotic strains have been found as well. The vagina is not the only place where probiotics are living. The uterus, fallopian tubes, and ovaries all have been shown to have a presence of live probiotics. Again, lactobacillus is the most prevalent.  


Similarly, the male reproductive tract contains probiotics, as demonstrated from the presence of bacteria in seminal fluid samples.  The bacterial communities (probiotic presence) found in the seminal samples are associated with semen health. In this regard, Lactobacillus may play a protective role; bacteria such as Anaerococcus, Pseudomonas, or Prevotella are mainly found in low‐quality sperm.


Healthy reproductive‐age women resent approximately one billion bacteria per gram of vaginal fluid with low diversity, mainly composed of one or few Lactobacillus species. Researchers have found that the vaginal microbiome of pregnant women who deliver at term is abundant in Lactobacilli. 


Evidence from several groups indicates that infertile patients harbor a differential reproductive tract microbiota (lower and/or upper) compared to healthy and fertile women.


The association between lack of a certain quantity and presence of certain probiotics (mainly lactobacillus) in the vagina has been associated with assisted reproduction failure and decreased pregnancy rates in IVF. Additionally, the presence of less-ideal bacteria like E. coli and streptococci has been related to lower implantation and pregnancy rates.  One study suggests that a high percentage of infertile patients subjected to ART present an abnormal endometrial bacterial profile.11


Several oral and vaginal probiotics are currently commercially available.  While I have never personally used vaginal probiotic suppositories (nor do I think I want to), it likely wouldn’t hurt anything.  





Probiotic supplements, like other dietary supplements, are unregulated by the US government.  Companies are not required to verify that what they are claiming is in their supplements are actually in their supplements! Yikes!  


So how can you tell that you are getting what you are paying for?


One good first-step is to make sure that the supplements you are choosing are third-party tested and verified.  Look for the following:

  •  USP verification seal.  Seeing the letters USP is not enough.  It must say that it is USP verified

  • NSF seal

  • Verify with consumer labs


Some bloggers advocate to try a milk test.  Basically they mix probiotics in with milk to see if the acid from the bacteria makes yogurt. They claim that if the milk stays liquid, then the probiotic you are using is dead. Although it would be a fun science-experiment, I don’t believe that this test is an accurate indicator. Some probiotics are enterically coated and are only active once they enter an acidic environment (i.e. your gut). Other probiotics are not actually acid-producing bacteria, and therefore would fail this test.


Using pharmacy-grade probiotics from a reputable source is a great start. 


Make sure you are taking an appropriate dose and take it consistently every day.


If this is too much to handle, food-sources of probiotics are always a good bet.  Foods like fermented vegetables, real yogurt/skyr, kefir, tempeh, miso, and pickles are all great choices.




A word on heat and probiotics.  Many strains of probiotics typically do not survive beyond 100 degrees Farenheit.  This is important to keep in mind in the summertime.  I recall when I was nursing my daughter and ordering her Vitamin D/lactobacillus reuteri drops via Amazon.  During the 100 degree weather in July, the package of drops were hot to the touch and I sent them back.  I did not believe that the probiotics survived sitting on a hot UPS truck for the entire day. I still wonder if Amazon turned around and sold that bottle to a different mom.


If there is an option to order probiotics with an ice pack, do it!  Don’t let your probiotics sit in the hot sun all day until you get home to bring your packages in, and question whether the probiotic was sitting on a hot truck.  Or buy them from a reputable store. Again, there are some strains that are more heat-resistant compared with others, but better be safe than sorry IMO.


I keep my family’s probiotics in the refrigerator.  I figure why not?  


Of course, you can always opt for food. Just make sure you are eating the probiotic-rich foods consistently, and that they contain the probiotic strain that your body needs. If you need help with food choice, probiotic selection, dosage, or specific strain, I am always happy to help!