Summary: New research finds that infants whose mothers had higher cortisol levels in late pregnancy tend to have earlier eruption of primary (milk) teeth. On average, babies of mothers with the highest cortisol concentrations had about four more teeth by six months than infants whose mothers had the lowest cortisol levels.
The study suggests that prenatal stress could accelerate aspects of early biological development, affecting mineralization and the timing of tooth eruption. Weaker but notable links were also observed between several other maternal hormones and the timing of tooth emergence, highlighting broader developmental questions to explore.
Key Facts:
- Cortisol link: Higher maternal cortisol in late pregnancy predicted a greater number of erupted primary teeth by six months of age.
- Accelerated development: Earlier teething may reflect faster biological aging related to prenatal stress exposures.
- Hormonal influences: Maternal sex and thyroid hormones showed weaker but statistically significant associations with eruption timing at later ages.
Source: Frontiers
Context on primary teeth: Children develop 20 primary teeth—10 in each jaw—which support chewing, speaking, and maintaining space for the later permanent dentition of 32 teeth. These milk teeth begin forming in the womb around the sixth week of gestation and typically erupt between about six months and three years after birth.
There is considerable natural variation in eruption timing, influenced by genetics, geography, nutrition, and overall infant health. The new study adds prenatal maternal stress hormones to the list of factors that appear to shape early dental development.
Researchers from the United States report these findings in Frontiers in Oral Health. According to corresponding author Dr. Ying Meng, associate professor at the University of Rochester School of Nursing, the analysis shows a clear association between higher stress-related hormone levels—especially cortisol—late in pregnancy and earlier eruption of primary teeth in the infant.
Study design and participants
The study followed 142 pregnant women from socioeconomically disadvantaged backgrounds who enrolled at the University of Rochester Medical Center between 2017 and 2022. Each participant provided saliva samples in the late second and third trimesters. Researchers measured concentrations of cortisol, estradiol, progesterone, testosterone, triiodothyronine (T3), and thyroxine (T4).
All births were full term. After delivery, dentist assessments of erupted primary teeth were performed at visits when the infants were approximately 1, 2, 4, 6, 12, 18, and 24 months old.
Demographically, about half of the mothers (53%) were employed and 60% had a high school education or less. Most (76%) were not first-time mothers, and a majority (59%) were not breastfeeding at six months. About 52% of the infants were African American. During pregnancy, roughly 36.6% of the women had a clinical diagnosis of depression or anxiety; however, those diagnoses were not directly associated with maternal hormone concentrations or infants’ tooth counts.
Patterns of tooth eruption
Eruption timing varied across the cohort. By six months, about 15% of infants had between one and six erupted teeth; by 12 months nearly all infants had some erupted teeth, and by 24 months roughly 25% had the full set of 20 primary teeth. A small subset (2.7%) experienced a rapid spurt of eruption between 12 and 18 months, while most infants followed a more gradual but irregular pattern. The number of teeth at early visits did not reliably predict counts at later visits.
Across the six hormones studied, women tended to exhibit either generally higher or generally lower-than-average concentrations, meaning hormone levels were correlated within individuals.
Main findings
The strongest association identified was between maternal cortisol measured late in pregnancy and infant tooth counts at six months. Infants born to mothers with the highest cortisol levels had, on average, about four more erupted teeth at six months than infants whose mothers had the lowest cortisol. The authors suggest several biological pathways that could explain this link, including alterations in fetal growth, mineral metabolism, and the activity of bone-forming and bone-resorbing cells (osteoblasts and osteoclasts). Cortisol can influence calcium and vitamin D regulation—both essential for tooth and bone mineralization.
In addition to cortisol, higher maternal levels of estradiol and testosterone were weakly associated with greater tooth counts at 12 months. Progesterone and testosterone showed modest positive associations with tooth counts at 24 months, and maternal T3 was weakly associated with counts at 18 and 24 months. Estradiol, progesterone, and testosterone have known roles in fetal growth and birthweight, which could help explain why elevated levels might modestly accelerate tooth eruption.
The authors emphasize that accelerated tooth eruption may signal broader shifts in early biological aging and development related to prenatal stress and socioeconomic disadvantage. They call for further research to identify which hormones or downstream pathways most directly drive alterations in eruption timing and what earlier eruption reveals about a child’s general health trajectory.
Key Questions Answered:
A: Elevated maternal cortisol in late pregnancy was associated with faster tooth eruption, producing more erupted teeth by six months.
A: Cortisol can alter fetal growth, mineral metabolism (including calcium and vitamin D), and the activity of bone-forming and bone-resorbing cells, which may influence tooth mineralization and timing.
A: Early eruption may reflect accelerated biological aging linked to prenatal stress and socioeconomic factors, and could serve as an early indicator warranting further developmental monitoring.
Editorial Notes
- This article was edited by a Neuroscience News editor.
- The journal article was reviewed in full by staff.
- Additional context and clarification were added for readers.
About this stress and neurodevelopment research news
Author: Mischa Dijkstra
Source: Frontiers
Contact: Mischa Dijkstra – Frontiers
Image: The image is credited to Neuroscience News
Original Research: Open access. “Prenatal maternal salivary hormones and timing of tooth eruption in early childhood: a prospective birth cohort study” by Ying Meng et al., published in Frontiers in Oral Health.
Abstract
Prenatal maternal salivary hormones and timing of tooth eruption in early childhood: a prospective birth cohort study
Background: The biological processes that determine the timing of tooth eruption are not fully understood. Evidence suggests that the prenatal maternal environment, and in particular stress exposures, may influence dental development, but few studies have examined prenatal stress-related hormones in relation to tooth eruption.
Methods: This prospective cohort study included 142 mother–child pairs to examine associations between prenatal stress, stress-related salivary hormones, and the number of erupted primary teeth. Maternal saliva collected in late pregnancy was analyzed for cortisol, estradiol, progesterone, testosterone, T3, and T4. Dentists counted erupted teeth at child visits through 24 months. Maternal diagnoses of depression and anxiety from medical records were used as a proxy measure of stress. Generalized linear models adjusted for relevant covariates were used to estimate associations.
Results: Eruption timing varied: about 15% of children had at least one erupted tooth by six months, and 25% had all 20 primary teeth by 24 months. Correlations in tooth counts across visits were modest. Several maternal hormones—including cortisol, estradiol, progesterone, testosterone, and T3—showed significant positive associations with the number of erupted teeth at specific visits (p < 0.05). Notably, higher prenatal cortisol was linked to more erupted teeth at six months, with an approximate average difference of four teeth between the lowest and highest cortisol levels.
Conclusion: Maternal salivary hormone concentrations measured in late pregnancy are associated with variation in primary tooth eruption during the first two years of life. These findings point to prenatal endocrine influences on early dental development and support further research into mechanisms and long-term implications.