Prenatal stress may speed up babies' first teeth

Most children grow all 20 of their primary teeth between six months and three years of age, but the timing can vary a lot. Genetics plays a role. So do geography and nutrition.

Now there is evidence that another influence starts even before birth. New research suggests that stress during pregnancy may speed up the arrival of a child’s first teeth.

The work focuses on mothers who gave birth at full term and brought their babies to regular dental checks during the first two years of life.

By comparing hormone levels in late pregnancy with how many teeth each child had at different ages, the study points to a connection that has not been shown before.

Factors that influence growth

The study was led by Dr Ying Meng, an associate professor at the School of Nursing of the University of Rochester.

The results center on 142 mothers from socioeconomically disadvantaged backgrounds in the U.S. The women enrolled through the University of Rochester’s Medical Center between 2017 and 2022.

In the late second and third trimesters, each participant provided a saliva sample.

Scientists measured six hormones: cortisol, estradiol, progesterone, testosterone, triiodothyronine, and thyroxine. These hormones influence growth, metabolism, and fetal development.

The team then followed every mother-child pair at one, two, four, six, 12, 18, and 24 months after birth. Dentists recorded which teeth had erupted at each visit.

Early baby teeth, unexpected patterns

Children normally reach these milestones in different ways, and this group was no exception.

By six months, 15 percent had between one and six erupted teeth. By 12 months, 97.5 percent had between one and 12. At 18 months, all children had teeth, ranging from three to 20.

At 24 months, a quarter had the full set of 20. A small number, 2.7 percent, had a sudden spurt between 12 and 18 months. Most showed a slower, uneven pattern. Early tooth counts did not predict later ones.

The parents in the study came from many backgrounds. About half, 53 percent, were employed. Sixty percent had a high school education or lower. For 76 percent, this was not their first child.

Most, 59 percent, did not breastfeed at six months. Roughly half of the children, 52 percent, were African-American.

Some women, 36.6 percent, had a diagnosis of depression or anxiety during pregnancy. These diagnoses did not match differences in hormone levels or tooth counts.

Hormone concentrations varied greatly from one mother to another. Women tended to show either higher-than-average or lower-than-average levels across all six measured hormones.

What cortisol reveals

Amid all of this variation, one pattern was clear. Children whose mothers had higher levels of cortisol in late pregnancy had more erupted teeth at six months of age.

Cortisol is often called a stress hormone. Infants of mothers with the highest levels had, on average, four more teeth at six months than infants of mothers with the lowest levels.

“Here we show that a mother’s higher levels of stress-related hormones, particularly of cortisol, during late pregnancy are associated with the earlier eruption of primary teeth in her infant,” said Dr. Meng.

“High maternal cortisol during late pregnancy may alter fetal growth and mineral metabolism, including the regulation of levels of calcium and vitamin D – both essential for mineralization of bone and teeth.”

Stress and biological aging

According to Dr. Meng, cortisol is also known to influence the activity of so-called osteoblast and osteoclast cells, responsible for building up, shaping, and remodeling bone.

Hormones shape many aspects of development, and cortisol may serve as one piece of a broader picture.

“These results are further evidence that prenatal stress can speed up biological aging in children,” said Dr. Meng.

“Premature eruption of teeth could thus serve as an early warning sign of an infant’s compromised oral development and overall health, associated with socioeconomic deprivation and prenatal stress.”

Other hormones, weaker patterns

The researchers also saw links between estradiol and testosterone levels in late pregnancy and the number of erupted teeth at 12 months. Those associations were weaker.

Similar modest links appeared for progesterone and testosterone at 24 months, and for triiodothyronine at 18 and 24 months.

Estradiol, progesterone, and testosterone play major roles in fetal growth and birthweight. When these levels run high, they may contribute to faster development, including earlier tooth eruption.

Baby teeth reflect early development

The work raises questions about how early stress affects lifelong health. Teeth are part of a child’s oral development, but they also reflect broader biological changes happening before birth.

Researchers continue to study how early life conditions shape development. Teeth provide a clear, measurable sign that something in that early environment has shifted.

As scientists explore these links, they hope to better support mothers during pregnancy and better understand how stress finds its way into childhood health.

The full study was published in the journal Frontiers in Oral Health.

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