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Are Cavities Contagious from Mom to Baby?

You’ve heard the warning before: Don’t share saliva with your baby. No sharing utensils, food, or toothbrushes. No “cutting” grapes in half with your own teeth. No cleaning the crud off the corner of her mouth with a little spit on your finger. No blowing on your baby’s hot food or tasting it yourself first. All of these things can spread mama’s saliva to baby and infect her mouth with cavity-causing bacteria.

I’ve heard these warnings, but all I can say is, “Seriously?” In my mind, a little saliva-sharing between mom and baby is unavoidable. I have tried. It wasn’t too difficult for the first few months of BabyC’s life, but then she started fish-hooking my mouth with her finger while she nursed, and it’s been down hill over since.

So what’s the deal? Are cavities contagious? If so, what can we do about it?

Mutans streptococci

Bacteria that colonize the mouth cause cavities, or dental caries. Mutans streptococci (MS) are the most common bacteria implicated, but several other species are also associated with caries. The bacteria consume food particles, particularly sugar and starch, and produce acid, which causes demineralization of the tooth.

We aren’t born with bacteria-infested mouths – we have to be infected. Cavities are contagious in the sense that MS can be passed from mom’s saliva to baby’s mouth, where they quickly set up shop. MS is detected in some infants within the first few months of life, even before their first teeth erupt, and studies conducted in the 1980’s identified mom as the primary source of bacterial colonization in an infant’s mouth [1]. Of course, you’ve got to wonder if a bit of colonization blame has shifted towards fathers or other caregivers since the 80’s, since fathers are sharing more of the balance of childcare these days.

Studies have also shown that children colonized with MS earlier in life have a greater risk of cavities in childhood. For example, Kohler et al. [2] studied 78 Swedish children, beginning at 15 months and continuing until age four. Of the children that were colonized with MS at two years of age, a full 89% had cavities by the time they were four. Among the children infected between ages three and four, only 36% had cavities at age four. Preventing or even just delaying colonization may protect children from later tooth decay, since soft baby teeth are extra-susceptible to decay in the first few years of life. Plus, I’m guessing (hoping) that dental hygiene becomes easier and more effective as kids get older.

Why worry about cavities in baby teeth? They’re going to fall out anyway, right? True, but there are good reasons to protect your baby’s teeth from decay:

  • Cavities cause pain. Enough said.
  • Healthy teeth are important for chewing food and speaking.
  • Dental work is expensive and can require general anesthesia in young children.
  • Children that suffer from dental caries in their primary teeth are at higher risk for caries in their permanent teeth [3, 4]. And if baby teeth are lost early due to decay, the spacing of permanent teeth can be affected.

Despite great attention to my oral hygiene, I have cavities. I had lots of them as a child, and my dentist usually catches one or two new small ones every few years. Chances are good that I’m infected with MS. What can I do to prevent their spread to BabyC and protect her from the legacy of tooth decay?

Because of the link between maternal infection with MS and the risk for early childhood caries, several studies have looked at interventions to reduce mom’s MS load. In one study, 77 first-time moms with infants 3-8 months old and with high infection rates of MS were randomized to control and intervention groups [5]. The intervention group received a dental decay prevention program that included oral hygiene and dietary counseling, teeth cleaning, fluoride treatment, and excavation of large cavities. The intervention was effective; it reduced mom’s salivary MS counts by 10-fold. At three years of age, children of the intervention moms had a 2.6-fold reduction in MS colonization and a 2.7-fold reduction in cavities. Kids in the intervention group still had fewer cavities than the control kids at age 7, several years after the intervention program ended [6]. At age 15, treatment differences in colonization and cavities were no longer statistically significant. However, children who were not yet colonized at age 3 had lower counts of MS and fewer cavities at age 15, demonstrating the risk of early colonization [7].

Xylitol gum has also been tested as an alternative approach to reducing maternal MS infection and thus, transmission to baby. Xylitol inhibits the growth of MS and decreases their ability to stick to teeth. To date, three studies have found that when mom chewed xylitol gum 2-3 times per day, beginning before baby’s teeth erupt or even during pregnancy, MS colonization of baby’s mouth was delayed and reduced [8-11] and caries were reduced at age 5 [9]. This approach is low-cost and an easy addition to good dental hygiene and care.

Other identified risk factors for early childhood MS infection have included nighttime nursing, early introduction of solid foods, exposure to sugar, and opportunities to share saliva (infant sucking on adult finger, sharing food, pre-tasting food). On the other hand, infants whose gums were cleaned daily had a lower incidence of infection [12].

Maternal MS infection isn’t the only factor determining colonization of a child’s mouth. However, reducing MS colonization is the first step a mom (or dad) can take to reduce a child’s risk of cavities. This research isn’t new, and I’m surprised that more pregnant women aren’t counseled on the impact of their oral hygiene on their child’s risk for cavities – an effect that may last a lifetime. As a public health message, I think this one is likely to be more effective and feel more doable than asking parents to never share food or drink with their young kids.

We’re doing everything we can to take good care of BabyC’s teeth. We do a lot of tooth brushing (with xylitol gel, for what it is worth), and we give her a fluoride supplement (our water is not fluoridated). We limit snacking and avoid foods with a lot of added sugar. But until now, I didn’t know that paying extra attention to my own teeth and even something as simple as chewing xylitol gum could make such a difference. It’s sort of a beautiful thing, actually. Take care of yourself, and your child will automatically benefit.

Based on the research I have found, here’s what you can do to reduce your MS infection rate and stop/slow the spread to your child:

  • See your dentist regularly for check-ups and cleanings, especially during pregnancy. Most dental procedures are safe during pregnancy, but check with your obstetrician to be sure.
  • Ask your dentist for a refresher on oral hygiene to be sure your daily routine is up to speed.
  • Beginning during pregnancy, chew xylitol gum several times per day. Look for products with xylitol as the first ingredient. Studies suggest that you need 5-6 grams of xylitol per day to reap the full benefits.
  • Minimize saliva sharing. Although I scoffed at this, the dose and frequency of MS exposure probably matter. A little saliva sharing may be unavoidable, but do what you can.

Do you worry about sharing saliva with your child?


1. Davey, A.L. and A.H. Rogers, Multiple types of the bacterium Streptococcus mutans in the human mouth and their intra-family transmission. Arch Oral Biol, 1984. 29(6): p. 453-60.

2.            Kohler, B., I. Andreen, and B. Jonsson, The earlier the colonization by mutans streptococci, the higher the caries prevalence at 4 years of age. Oral Microbiol Immunol, 1988. 3(1): p. 14-7.

3. al-Shalan, T.A., P.R. Erickson, and N.A. Hardie, Primary incisor decay before age 4 as a risk factor for future dental caries. Pediatr Dent, 1997. 19(1): p. 37-41.

4. Alm, A., et al., Prevalence of approximal caries in posterior teeth in 15-year-old Swedish teenagers in relation to their caries experience at 3 years of age. Caries Res, 2007. 41(5): p. 392-8.

5. Kohler, B., I. Andreen, and B. Jonsson, The effect of caries-preventive measures in mothers on dental caries and the oral presence of the bacteria Streptococcus mutans and lactobacilli in their children. Arch Oral Biol, 1984. 29(11): p. 879-83.

6. Kohler, B. and I. Andreen, Influence of caries-preventive measures in mothers on cariogenic bacteria and caries experience in their children. Arch Oral Biol, 1994. 39(10): p. 907-11.

7. Kohler, B. and I. Andreen, Mutans streptococci and caries prevalence in children after early maternal caries prevention: a follow-up at eleven and fifteen years of age. Caries Res, 2010. 44(5): p. 453-8.

8. Nakai, Y., et al., Xylitol gum and maternal transmission of mutans streptococci. J Dent Res, 2010. 89(1): p. 56-60.

9. Soderling, E., et al., Influence of maternal xylitol consumption on acquisition of mutans streptococci by infants. J Dent Res, 2000. 79(3): p. 882-7.

10. Soderling, E., et al., Influence of maternal xylitol consumption on mother-child transmission of mutans streptococci: 6-year follow-up. Caries Res, 2001. 35(3): p. 173-7.

11. Thorild, I., B. Lindau, and S. Twetman, Salivary mutans streptococci and dental caries in three-year-old children after maternal exposure to chewing gums containing combinations of xylitol, sorbitol, chlorhexidine, and fluoride. Acta Odontol Scand, 2004. 62(5): p. 245-50.

12. Wan, A.K., et al., Oral colonization of Streptococcus mutans in six-month-old predentate infants. J Dent Res, 2001. 80(12): p. 2060-5.

  1. Hippo74 #

    Interesting read. I am though interested in your statement that “Other identified risk factors for early childhood MS infection have included nighttime nursing”. I was under the impression from what I have read and from my dentist that breast milk is not cariogenic on its own, only when in contact with other foodstuffs in the mouth. Therefore if exclusively breast feeding there should be no increased risk and if teeth are brushed well post food prior to bed, breast milk after this will have no cariogenic effect. Obviously the same cannot be said for formula feeding over night, but I was lead to believe that there was a definate distinction between the two.


    June 12, 2012
    • In the study I cited in this article, night nursing was associated with MS colonization, but it did not show a causal relationship. I haven’t looked closely at other studies on the cariogenicity of human milk, but Squintmom wrote an article on it. She discusses a study that measured cariogenicity of breast milk compared to other substances, including sugar, soda, and cow’s milk. Breast milk was moderately cariogenic – less so than sugar or soda but more so than cow’s milk.

      My guess is that night nursing is a bigger problem for baby teeth than formula-feeding in part because breastfed babies tend to wake more to feed during the night during the second half of the first year, when teeth are really coming in, then formula-fed babies. (At this age, I think this is likely a parenting style difference more than anything else.)

      Thanks for the comment. I know there is a lot of confusion and controversy around this topic, and not all that much evidence either way!


      June 12, 2012
  2. Barbara #

    I used to work in a general dentists office, and it’s really not a big deal as long as your take care of their teeth and teach good habits, just be careful because decay on a baby tooth can actually transfer to the new tooth while it’s pushing up agains the baby one. Happens quite often.


    June 14, 2012
  3. dnvrmama #

    Thank you for another great post. This is something I worry about probably more than I should, so I find the post particularly interesting. Like you, starting with the finger hook in the mouth, we’ve gone downhill.

    You mentioned that you use a fluoride supplement since your water isn’t fluoridated. I’m curious to know more about fluoride’s role in preventing baby cavities. The dentist told us to go ahead and use a fluoride toothpaste at 1yr (just a tiny, less-than-pea-sized portion). On the other hand, I’ve heard that fluoride is bad for infants if ingested and doesn’t really help with tooth decay if ingested. So there seems to be some conflicting information. says
    “The benefit is so great for children because when fluoride is taken internally, it is incorporated into teeth as they grow. Fluoride makes the enamel coating of teeth stronger and more resistant to decay.”

    and here I see:
    “Fluoridated water is no longer recommended for babies. In November of 2006, the American Dental Association (ADA) advised that parents should avoid giving babies fluoridated water (3). Other dental researchers have made similar recommendations over the past decade (4).

    Babies exposed to fluoride are at high risk of developing dental fluorosis – a permanent tooth defect caused by fluoride damaging the cells which form the teeth (5). Other tissues in the body may also be affected by early-life exposures to fluoride. According to a recent review published in the medical journal The Lancet, fluoride may damage the developing brain, causing learning deficits and other problems (6)”

    If you have time, maybe you could shed some light on this for me.


    June 17, 2012
  4. suzy #

    Great post – my husband is a pediatric dentist and he was very impressed with your research and recommendations. He wishes that more parents would follow this advice! One small note was that he doesn’t agree on the xylitol gum recommendation, as his take is that in order to make a difference you’d have to chew so much as to risk TMJ and some rather explosive GI symptoms, but he thought the rest of the post was spot on. I really appreciate the research that you do on parenting issues and look forward to your posts.


    June 28, 2012
  5. Connie #

    I know this reply is rather late, but as a pediatric dentist, I just wanted to say THANK YOU for including this. It’s really difficult to get our message across, even to our pediatrician and general dentist colleagues, that healthy habits must start very early on! In fact, our first dental appointment (at 1 yr of age) is primarily educational- we guide parents into good habits and teach them how to take care of their baby’s gums/teeth….Baby teeth are so important and I want to shout that from the top of a mountain sometimes! Thank you, thank you, thank you!


    August 27, 2015

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