Maintaining good oral hygiene may be especially important during pregnancy.
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“You give birth to a child, you lose a tooth,” as the proverb goes. Pregnancy it's known to be associated with an increased risk of dental problems, but we're not entirely sure why. Now, researchers have found that the oral microbiome changes while a woman is expecting, becoming less diverse and potentially more prone to inflammation.
Hormonal upheaval during pregnancy usually accused of higher risk of conditions such as gum disease and tooth decay. A common idea is also that the fetus takes calcium from the mother's teeth, but this is not supported by evidence.
Disturbance of the oral microbiome, which consists of more than 700 species of bacteriamay cause dental problems regardless of whether a woman is pregnant. But Yoram Luzun from Bar-Ilan University in Israel and colleagues wanted to understand whether this generally stable ecosystem changes during pregnancy, so they collected saliva samples from 346 Israeli women at 11–14 weeks, 24–28 weeks and 32–38 weeks of pregnancy, representing all three trimesters.
The researchers saw a decline in species diversity in saliva samples as early as the transition between the first and second trimesters of pregnancy, and then gradually decreased throughout the rest of pregnancy. Key features included a decline in the species' numbers. Akkermansia mucinifilaoften perceived as “good bacteria” and an increase in the bacteria Gammaproteobacteria and Synergistota, which are associated with inflammation.
“Usually the oral microbiome is stable, but diversity slowly decreases over many years,” says Luzun. “Pregnancy is a fast forward of this very slow evolution. You can see changes that usually take many years to happen in just nine months.”
There are many possible reasons why these changes occur – although they are generally small. “You'll have a lot going on during pregnancy, like hormonal changes and inflammation, which will also change the microbiome,” says Lindsay Edwards at King's College London. “And obviously, when you're pregnant, you change your diet a lot. You may also feel nauseous and refuse to eat, and you may also want to stop taking your medications if you know you're pregnant. All of these can have consequences.”
Women completed dietary and health questionnaires, which allowed the researchers to identify distinctive but similar effects among some women, such as those who said they followed a gluten-free diet, took antibiotics, were stressed, or were smokers or former smokers. “Most women quit smoking during pregnancy, but you see an impact on the microbiome from the fact that they smoked maybe nine months ago,” Luzun says. “It has a really long-term effect.”
Comparable changes were evident in a second experiment, in which researchers examined the oral microbiome of 154 pregnant Russian women in the second and third trimesters of pregnancy.
While pregnancy is known to increase the risk of dental problems, Luzun doesn't necessarily think changes in the oral microbiome are behind it, given that such problems can start very early in pregnancy. “I can't say for sure whether all these microbiome changes are positive or negative, but they are definitely happening quickly,” he says.
However, Edwards says microbial changes may be a factor, noting that saliva also becomes more acidic during pregnancy, changing the types of bacteria.
Valentina Biagioli at the University of Genoa in Italy say changes in the oral microbiome and hormone levels throughout the body may play a role as they interact and influence each other. “There is plausible biological rationale linking the observed changes in the oral microbiome to the most common dental problems encountered during pregnancy, including tooth loss,” she says.
Disorders of the oral microbiome have been associated with pregnancy complicationsso if we establish what the optimal version of this ecosystem looks like, it can be used to assess how pregnancy is progressing. “Once we have a baseline of the oral microbiome during pregnancy, it can be used to identify abnormalities,” Luzun says.
We're also learning more about this microbiome's role in the immune system, which can impact the health of both. pregnant women and their fruits. “The microbiome helps educate your immune system, and it's a two-way communication,” says Edwards.
Better understanding of how to maintain oral microbiome – for example, through good oral hygiene and a varied, nutrient-rich diet – can have long-term effects. “Changes in the microbiome may determine the inflammatory status of the parents and help strengthen the child's immune system, which either promotes long-term health or potentially influences allergy risk, susceptibility to infections, or the development of long-term chronic inflammatory conditions,” says Edwards.
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