How Early Can a Baby Start Teething: Key Facts

Most babies cut their first tooth somewhere between four and thirteen months of age, with the average landing around six to seven months. But the earliest a baby can technically start teething is before birth. A small number of infants are born with one or two teeth already visible, a phenomenon that, while rare, is well-documented in medical literature and has been observed for centuries. The range of “normal” is much wider than many parents expect, and the timing depends on a tangle of factors from genetics and sex to birth weight and nutrition.

The Typical Window for a First Tooth

A prospective study tracking healthy infants found that the first tooth appeared anywhere from four to thirteen months of age. By six months, roughly a quarter of infants had at least one tooth. By nine months, that figure jumped to about 85 percent.¹ Another large cohort placed the average age of first tooth eruption at about 30 weeks, or just past seven months, with a standard deviation wide enough to comfortably include babies who pop a tooth at four months and those who wait past their first birthday.²

The teeth almost always arrive in the same general order: lower central incisors first (the two bottom-front teeth), followed by the upper central incisors, then the lateral incisors to either side. The full set of twenty baby teeth usually finishes coming in somewhere between age two and three. By a child’s first birthday, the average count is about six teeth, give or take a couple.² If your baby has only two or three at twelve months, that is still within the normal range and not a sign of developmental trouble on its own.

Born with Teeth

The absolute earliest a baby can have teeth is at birth. Teeth present at delivery are called natal teeth; those that break through in the first thirty days of life are neonatal teeth. The distinction matters mostly to clinicians deciding what to do about them, but to parents, both are startling. Natal teeth are roughly three times more common than neonatal teeth, though neither is particularly common.³

How rare are we talking? A pilot study at a single hospital screened over 4,300 newborns and found exactly four with natal teeth, which gives a sense of scale.⁴ Published estimates across different populations generally place the occurrence somewhere between one in every 1,000 to one in every 6,000 births, depending on the study. The teeth almost always show up in the lower front region of the mouth, and they frequently appear in pairs.

Most natal and neonatal teeth are genuine baby teeth that have erupted early rather than extra “supernumerary” teeth. That distinction matters because extracting a real baby tooth means it will not be replaced until the permanent one arrives years later, potentially affecting spacing. Extraction is usually reserved for teeth that are extremely loose and pose an aspiration risk, or that interfere with breastfeeding. In a tertiary care review of 33 babies with natal or neonatal teeth, the main local complication observed was Riga-Fede disease, an ulceration on the underside of the tongue caused by the tooth rubbing against it during sucking.⁵ In some cases a positive family history was present, suggesting a genetic component. When complications do arise, they can include difficulty feeding, tongue injury, and inadequate nutrient intake if the problem goes unmanaged.³

What Influences When Teeth Come In

If two babies born on the same day can have their first tooth nine months apart, something has to explain the gap. Several factors have been studied, and the picture is more complex than simple genetics alone.

Sex. Boys tend to get teeth slightly earlier than girls. One large cohort found that boys cut their first tooth about a week ahead of girls on average, and by twelve months they had a marginally higher tooth count.² The difference is modest and swamped by individual variation, but it has been replicated across studies.

Birth weight. Heavier babies at birth tend to get teeth a bit sooner. A prospective cohort study found a statistically significant inverse relationship between birth weight and the timing of first tooth eruption: higher birth weight predicted earlier appearance.⁶ This aligns with broader findings about growth and dental development tracking together.

Nutrition and growth percentiles. How a baby is fed in the first year appears to matter. In the same Turkish cohort that mapped the four-to-thirteen-month range, infants with height and weight percentiles below the 50th mark, and those fed cow’s milk or formula rather than breast milk in the first year, were less likely to have a tooth by six months.¹ These factors were identified as independent predictors, meaning each one contributed on its own after adjusting for the others.

Prenatal vitamin D. Parents sometimes wonder whether the mother’s vitamin D status during pregnancy affects teething. One prospective cohort found no significant correlation between maternal vitamin D levels in the first or second trimester and when the baby’s first tooth erupted.⁶ So while vitamin D matters for many aspects of bone health, its prenatal level does not seem to push teething earlier or later in any measurable way.

Teething in Babies Born Early

Premature babies sometimes worry their parents with what looks like delayed teething. A six-month-old preemie born at 32 weeks might not have any teeth yet, while full-term babies the same calendar age are already drooling around new incisors. But the delay is largely an artifact of calendar math rather than a genuine dental problem.

Studies comparing preterm and full-term infants have found that when you use chronological age (time since birth), preterm babies are significantly delayed in first tooth eruption. However, when you calculate corrected age (time since the original due date), the difference disappears.⁷ A separate study confirmed the same pattern: the delay tracks with prematurity itself, not with any underlying problem in how the teeth are developing.⁸ In plain terms, a baby born two months early will likely start teething about two months “late” by the calendar, and that is completely expected.

For parents of preemies, the practical takeaway is to judge teething milestones by corrected age rather than birth date, at least through the first couple of years. Pediatricians typically do this for most developmental milestones anyway. If teeth are still absent well past the corrected-age window, that’s when further evaluation might be warranted, but it’s rarely the case for prematurity alone.

Does Teething Really Cause Fever

This is one of the most persistent beliefs in parenting, and the evidence is more nuanced than either a flat “yes” or “no.” A classic study examined the twenty days before the eruption of the first tooth in 46 healthy infants, based on mothers’ daily temperature reports. On the actual day the tooth broke through, 20 of the 46 infants had a temperature above 37.5°C. But in the preceding two to three weeks, only about seven or fewer infants on any given day hit that mark.⁹

So there does seem to be a modest bump in temperature around the day a tooth appears. The problem is that 37.5°C is barely above normal body temperature, and most pediatricians define a true fever as 38°C or higher. A slight rise in temperature on eruption day is plausible given the local inflammation in the gums, but a high fever, diarrhea, or significant illness should not be chalked up to teething. The same study emphasized the danger of attributing fever to teething, because doing so can lead parents to miss infections or other conditions that actually need treatment.⁹ A safe rule: if the temperature climbs above 38°C or your baby seems genuinely unwell, treat it as a potential illness, not a teething symptom.

How a Tooth Actually Pushes Through

Baby teeth begin forming in the jaw long before birth. By the time the tooth is ready to erupt, the biological machinery involved is surprisingly active. Research has shown that the dental follicle, the dense connective tissue surrounding each developing tooth, is the key driver. Without the follicle, neither the bone resorption above the tooth (which clears a path) nor the bone formation below it (which pushes the tooth upward) can happen.¹⁰

Early in eruption, cells accumulate in the upper part of the follicle that are capable of breaking down bone, while the lower part of the follicle undergoes rapid cell growth and responds to growth factors that help drive the tooth upward. This is why a tooth erupts in one direction and not another: different parts of its surrounding tissue are doing fundamentally different jobs. The process is slow and intermittent, which is why teething symptoms often come and go over days or weeks before a tooth actually becomes visible.

How New Teeth Change the Mouth

A baby’s mouth before teeth arrive is a very different environment from the mouth of a toddler with a row of incisors. The eruption of teeth introduces hard surfaces that bacteria can colonize, and the resulting shift in the oral microbiome is substantial. A longitudinal study tracking infants from the pre-dentition stage through full eruption of the eight front teeth found that microbial diversity in both saliva and dental plaque changed dramatically during that period.¹¹ Interestingly, the later eruption of primary molars did not cause a comparable shift, suggesting that the initial introduction of any tooth surface is what really reshapes the microbial community.

This matters because the bacteria that colonize teeth early can influence cavity risk later. It is one reason pediatric dentists recommend starting oral hygiene before the mouth is even full of teeth, and why the first dental visit is generally suggested around a child’s first birthday or within six months of the first tooth appearing.

Caring for Teeth That Show Up Early

Whether your baby cuts a tooth at four months or is born with one, cleaning it right away is worthwhile. Plaque begins accumulating on tooth surfaces as soon as they appear, and bacteria that cause decay can establish themselves early. A study of high-caries-risk infants aged eight to fifteen months found that both an infant tooth wipe and a conventional brush significantly reduced plaque levels, but parents found the wipe easier to use, and babies tolerated it better, particularly at nighttime after feeding.¹² For parents of very young infants with a tooth or two, a soft damp cloth wiped over the tooth after feeds can serve the same purpose.

When it comes to soothing teething discomfort, the market is crowded with gels, rings, and homeopathic drops. An in-vitro study comparing several popular teething gels found wide variation in cytotoxicity, with some products showing much higher toxicity to cells than others.¹³ That study is lab-based rather than clinical, so it does not directly tell you which gel is “safest” in your baby’s mouth, but it does underscore that not all teething gels are equivalent in their biological activity. The U.S. FDA has warned against teething products containing benzocaine (which can cause a rare but serious blood condition in infants) and against homeopathic teething tablets that have been linked to adverse events. Chilled (not frozen) teething rings and gentle gum massage remain the options with the best safety profile for very young babies.

When Early or Late Teething Warrants a Closer Look

A first tooth appearing at three or four months is early but not alarming. Natal teeth present at birth deserve evaluation simply because of the feeding complications and the small aspiration risk if the tooth is very loose, but they are not a sign of systemic disease in the vast majority of cases. Some conditions such as certain hormone disorders, genetic syndromes, and nutritional deficiencies can cause either very early or very late eruption, but these are almost always accompanied by other signs that a pediatrician would notice independently.

On the late side, most dentists do not consider the absence of teeth concerning until past about thirteen months of age, which is the upper end of the normal range documented in cohort studies.¹ Even then, isolated late teething in an otherwise healthy, growing child is more likely a family trait than a medical problem. The first step is usually a dental X-ray to confirm the teeth are present in the jaw and simply taking their time.

The Emotional Side of Early Teething

For first-time parents especially, teething can feel overwhelming. The combination of a fussy baby, disrupted sleep, and uncertainty about what is normal and what signals a problem turns a routine developmental milestone into a source of real anxiety. Research has characterized teething as a “daunting problem” for parents navigating it for the first time, and the commercial market around teething remedies feeds into that anxiety with products promising relief that may not deliver and may carry their own risks.

If your baby starts teething unusually early, the practical demands compound. A three-month-old with a tooth is still months away from solid food and may be exclusively breastfed, which means dealing with a sharp new incisor during nursing. Positioning adjustments, ensuring a deep latch, and applying lanolin to sore spots are often enough to get through the transition. Natal teeth that cause persistent tongue ulceration (Riga-Fede disease) can sometimes be managed by smoothing the tooth’s edge rather than extracting it, preserving the tooth while protecting the soft tissue.⁵

Keeping a simple log of when symptoms appear and when teeth actually break through can help you separate teething discomfort from illness, calibrate your expectations for subsequent teeth, and give your pediatrician useful information at well-child visits. Teeth generally arrive in waves separated by weeks or months of quiet, so the fussy periods are temporary even when they feel relentless.

1
PubMed. Factors affecting the timing of teething in healthy Turkish infants: a prospective cohort study
2
PubMed Central. Maternal and early life factors of tooth emergence patterns and number of teeth at one and two years of age
3
PubMed Central. Natal and neonatal teeth: an overview of the literature
4
PubMed Central. Incidence of Natal Teeth in Newborns in Government Medical College and Hospital, Chengalpattu: A Pilot Study
5
PubMed Central. Natal and Neonatal Teeth: A Tertiary Care Experience
6
PubMed Central. Association of prenatal vitamin D concentration with the eruption time of the first primary tooth: A prospective cohort study
7
PubMed Central. The influence of gestational age and birth weight of the newborn on tooth eruption
8
Egyptian Pediatric Association Gazette. Relationship between gestational age, birth weight and deciduous tooth eruption
9
PubMed Central. Fever associated with teething
10
PubMed. The basic and applied biology of tooth eruption
11
PubMed Central. Maturation of the oral microbiota during primary teeth eruption: a longitudinal, preliminary study
12
Pediatric Dentistry. The Effectiveness of a Novel Infant Tooth Wipe in High Caries-risk Babies 8 to 15 Months Old
13
Head & Face Medicine. Cytotoxic and antifungal effects of different teething oral gels: an in-vitro study