Prenatal stress may accelerate the arrival of a baby’s first teeth, according to new research. While it’s common for children to grow all 20 of their primary teeth between six months and three years of age, the timing can vary significantly, influenced by genetics, geography, and nutrition. Now, scientists have uncovered evidence of another factor at play even before birth. The study, led by Dr. Ying Meng, an associate professor at the University of Rochester, found that stress during pregnancy may expedite the eruption of a child’s first teeth. The research focused on 142 mothers from socioeconomically disadvantaged backgrounds in the U.S., who enrolled through the University of Rochester’s Medical Center between 2017 and 2022. During the late second and third trimesters, participants provided saliva samples, and scientists measured six hormones: cortisol, estradiol, progesterone, testosterone, triiodothyronine, and thyroxine. These hormones influence growth, metabolism, and fetal development. The team followed each mother-child pair at various intervals after birth, recording the eruption of teeth at each visit. The study revealed unexpected patterns. By six months, 15% of children had between one and six erupted teeth, and by 12 months, 97.5% 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, with a small percentage (2.7%) showing a sudden spurt between 12 and 18 months. Most exhibited a slower, uneven pattern. Interestingly, early tooth counts did not predict later ones. The study’s participants came from diverse backgrounds, with varying employment and educational levels. Most (59%) did not breastfeed at six months, and roughly half (52%) were African-American. Some women (36.6%) had a diagnosis of depression or anxiety during pregnancy, but these diagnoses did not correlate with hormone levels or tooth counts. Hormone concentrations varied widely among participants. Children whose mothers had higher cortisol levels in late pregnancy had more erupted teeth at six months. Cortisol, often referred to as a stress hormone, played a significant role. Infants of mothers with the highest cortisol levels had, on average, four more teeth at six months than those with the lowest levels. Dr. Meng explained that high maternal cortisol during late pregnancy may alter fetal growth and mineral metabolism, including calcium and vitamin D regulation, both essential for bone and tooth mineralization. According to Dr. Meng, cortisol also influences the activity of osteoblast and osteoclast cells, responsible for bone building and remodeling. The study highlights the potential of early tooth eruption as a warning sign of compromised oral development and overall health, associated with socioeconomic deprivation and prenatal stress. While the research found links between estradiol, testosterone, progesterone, and triiodothyronine levels and tooth eruption, these associations were weaker. The study raises intriguing questions about the long-term impact of early stress on health. Teeth, being part of a child’s oral development, also reflect broader biological changes occurring before birth. As scientists continue to explore these connections, they aim to enhance support for mothers during pregnancy and better understand the role of stress in childhood health. The full study was published in the journal Frontiers in Oral Health.