By Dr. Liji Thomas, MD Reviewed by Lauren Hardaker Nov 20 2025 A new birth cohort study reveals that a mother’s stress-related hormones in late pregnancy, especially cortisol, may quietly influence when her baby’s first teeth appear, uncovering a surprising link between prenatal biology and early childhood development. Study: Prenatal maternal salivary hormones and timing of tooth eruption in early childhood: a prospective birth cohort study. Image credit: Shevtsova Yuliya/Shutterstock.com