The Myth of the Sterile Womb

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Before Microbirth- Symbiotic Bacteria in Pregnancy

Unlike the popular belief that vaginal birth is the main way to populate a newborn´s body with maternal symbiotic bacteria, seeding actually begins with implantation and pregnancy and is further reinforced with vaginal birth and breastfeeding. A baby is not growing in a perfectly sterile environment until birth, but on the contrary is surrounded and supported by several different bacterial communities throughout pregnancy, which reside in different organs of the mother

Before Microbirth- Symbiotic bacteria in pregnancy

Alternative health communities praise the benefits of vaginal birth for establishing a health bacterial flora in the body of newborn babies. The documentary "Microbirth" presents up-to-date scientific evidence about the long-lasting health effects that babies reap when delivered as nature intended or during a positive c-section [In a positive c-section, a sterile gauze is inserted into the mother´s vagina for up to an hour and upon surgical delivery is used to wipe the newborn´s body and head, in an effort to simulate vaginal birth and donate maternal bacteria]. Understanding the importance of seeding the baby with maternal symbiotic bacteria should be basic knowledge for doctors, midwives and parents alike because it truly has the potential to improve the health of the future generations. "Microbirth" is a grand and very necessary step into pushing this essential knowledge into mainstream medical practice.

But in order to get the full picture of when and how bacterial seeding of babies happens we should really go a few steps further than the truths presented in "Microbirth". Or more specifically a few steps backwards, at least in time. This is because seeding a baby with maternal symbiotic bacteria does not start with a vaginal birth or a positive C-section at all. It all begins with conception and pregnancy. Unlike the outdated notion that a baby is growing in a perfectly sterile environment until birth, we now know that the baby is surrounded and supported by several different bacterial communities, which reside in different organs of the mother. Research shows that when pathogenic bacteria dominate the maternal organs, pregnancy complications become more frequent.

If the first bacterial seeding happened during birth, then we would expect meconium (baby´s first poo) to be essentially sterile, which we already have scientific proof that is not true. Therefore, somewhere along pregnancy, the baby interacts with maternal bacteria and receives the first sample of these lifelong, tiny buddies. Instead of considering birth as the only seeding event that donates maternal symbiotic bacteria to the baby, we need to understand that populating the baby´s body with bacteria is a multi-step process that begins with implantation of the fertilized egg, progresses throughout pregnancy and is finalized when the baby stops breastfeeding.

The baby receives and interacts continuously for the duration of the pregnancy with maternal bacteria and, later, vaginal birth and hopefully breastfeeding further reinforce and stabilize the first phase of seeding. These are all important and necessary steps for creating a healthy baby; it takes many months and conscious diet and lifestyle choices. Therefore, maintaining a healthy flora in the mother during pregnancy (by actively optimizing pregnancy probiotic / prebiotic intake and supporting beneficial bacteria) is the very first step for ensuring a healthy flora for the baby. Encouraging a vaginal birth or a positive c-section come second and breastfeeding third.

Important bacterial communities during pregnancy

Uterus and placenta

In terms of anatomy and physiology, the uterus and placenta are the most important organs that affect the baby from conception throughout pregnancy. In both cases, our knowledge about bacteria actually living in these organs is quite new, especially for the placenta. The bacteria in the uterus are freely swimming in the amniotic fluid during pregnancy, so these microorganisms are practically in touch with the growing baby. Unsurprisingly, when pathogenic bacteria dominate this sensitive environment, pregnancy complications become more frequent.

The available research on both the uterus and the placenta has shown that both of them contain bacterial communities that are more similar to the flora of the mouth than that of the vagina, despite the physical distance between them. Perhaps, this is why seemingly irrelevant health problems, such as serious gum infection (periodontitis), are known to increase the risk for pre-term birth [delivery before 37 weeks of gestation] and pregnancy complications. The beginning of our gastrointestinal system seems to be unexpectedly important for the wellbeing and bacterial balance of babies.

We have known the existence of symbiotic bacteria in the gut and vagina for decades, but the placenta is the newest member to the list of bacterial homes. The truth is that although the placenta is one of the most important organs for the wellbeing of the growing baby, our knowledge about it is still quite limited. What was once thought to be a sterile organ actually harbors a unique bacterial community. While the presence and origin of placenta bacteria is a brand new scientific finding that is being intensely investigated, research is starting to highlight the role of this community in healthy pregnancy and potential complications.

A 2015 study published in the Journal of Obstetrics and Gynecology research found that women with pre-eclampsia (characterized by high blood pressure and protein in urine) have placentas rich in pathogenic bacteria usually associated with gastrointestinal and respiratory infections or serious gum infection (periodontitis). We also know that the bacteria of the placenta are somehow involved in or indicate pre-term birth, because the bacterial populations in pre-term and full-term placentas are quite different.


The vagina is of course another organ of major importance for the baby´s bacterial seeding, but not only during birth. Research shows that vaginal bacterial flora is actually very important during pregnancy as well, since vaginal infections are a leading cause of preterm birth. Under normal circumstances, the vagina is characterized by, but definitely not restricted to, the popular and very beneficial bacteria called Lactobacilli. These bacteria produce lactic acid, which is responsible for the low vaginal pH actively keeping pathogenic bacteria at bay.

A fascinating fact about vaginal bacterial flora is that it responds and changes significantly during pregnancy and then gradually shifts back to a pre-pregnancy status after birth. More specifically, non-pregnant women have a greater variety of bacterial species, while in pregnant women Lactobacilli super-dominate the bacterial landscape. This is believed to offer a more stable and robust bacterial protection against dangerous pathogens and vaginal infections. And this is where we can see that vaginal bacteria can affect the baby way before birth. Whenever Lactobacilli do not dominate sufficiently the vagina, infections are more frequent and when Lactobacilli are replaced by potential pathogens, the risk for pre-term birth is sharply increased. We even know specific pathogenic bacterial species whose presence in the vagina is associated with preterm birth. These bacteria have not only been found in the vagina however, but also in umbilical cord samples, placenta, amniotic fluid and even baby tissues.


Intestinal bacteria were the first to be recognized for their immense role in health and disease. When it comes to pregnancy, balanced gut flora is believed to help the mother´s body adapt better to the dramatic changes that are part of a successful pregnancy. For example, it is well known that changes in the gut bacteria can prepare the ground for the development of gestational diabetes. At the same time, intestinal infections are suspected to be at least partially responsible for pre-term birth.


When it comes to the process of seeding the baby´s body with maternal symbiotic bacteria, we are witnessing the creation of a brand new paradigm, based on state-of-the-art scientific evidence. There are many bacterial communities important for the baby´s wellbeing during pregnancy and beyond. When bacterial balance is lost (=infection) during pregnancy, the risk for complications increases, to the point that pre-term birth is (at least partially) considered a microbial disease. The bacteria in the uterus, vagina and placenta practically surround the developing fetus and collectively determine which types of bacteria will be seeded in the baby´s body. From a microbiological point of view, the fertilized egg is embedded during implantation in the uterus, an already established bacterial community, whose composition depends on the mother´s previous diet, lifestyle and apparently oral health. The role of the vagina is not just about birth anymore. Ideally, vaginal bacteria partially safeguard microbiological balance which is necessary for a full-term pregnancy. The mouth unexpectedly shows up as a significant reservoir of bacteria, which populate the organs closer to the baby. Finally, the gut also seems to affect indirectly the course of pregnancy and baby´s wellbeing, since intestinal infections can pave the way to preterm birth.


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Disclaimer: This article is not intended to provide medical advice, diagnosis or treatment. Views expressed here do not necessarily reflect those of GreenMedInfo or its staff.

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