Embryology · Teratology and prenatal diagnosis
Tetracyclines and aminoglycosides !
- Teratogen
Two antibiotic groups with known fetal effects: tetracyclines stain the teeth and aminoglycosides can damage hearing.
Updated 2026-11-01
See it in 3D: Upper right central incisor · Cochlea · Vestibulocochlear nerve (VIII)
What it is
Tetracyclines bind calcium and are laid down in mineralizing teeth and bone, so they stain the primary teeth and disturb enamel. Some aminoglycosides, especially streptomycin, damage the fetal inner ear and can cause irreversible bilateral deafness. Other antibiotics, by contrast, are used in pregnancy when the benefit justifies it; the choice is made by the treating professional.
Key facts
- Tetracyclines can also cause severe liver damage in the pregnant woman.
- Fluoroquinolones damage cartilage in animal studies.
- Tetracycline tooth staining is permanent.
- Aminoglycoside ototoxicity affects the hair cells of the cochlea.
- A fetal-period example: these are functional or late-maturing tissue injuries, not first-trimester malformations.
Critical period and mechanism
- Critical period for tetracyclines: from the second trimester, when tooth and bone mineralization begins.
- They form complexes with calcium and are built into forming dentine, enamel and bone.
- Aminoglycosides: cross the placenta and accumulate in the fluid of the fetal inner ear.
- There they damage the cochlear hair cells and the vestibulocochlear nerve.
Prevention
- The choice of antibiotic in pregnancy is made by the treating professional according to the infection and stage.
- Avoiding self-medication with antibiotics in pregnancy.
- Newborn hearing screening after aminoglycoside exposure.
What it does to the embryo and fetus
- Yellow or brown primary teeth, defective enamel.
- Slowed bone growth with high exposures.
- Congenital bilateral sensorineural deafness (streptomycin).
- Severe neonatal jaundice from sulfonamides late in pregnancy.
Test yourself
Think of the answer, then tap the question to see it.
Why do tetracyclines stain the baby's teeth?
They chelate calcium and are laid down in the primary teeth as they mineralize, from the second trimester.
Which aminoglycoside is the classic cause of congenital deafness?
Streptomycin, which damages the cochlea and vestibulocochlear nerve bilaterally and irreversibly.
What risk do sulfonamides carry near term?
They displace bilirubin from albumin and raise the newborn's risk of kernicterus.
See it in 3D
The structures of Durgical's 3D anatomy where it is found.
Related
- Teeth
- Ear: inner, middle and external ear
- Congenital hearing loss, microtia and preauricular pits
- Principles of teratology: critical periods, dose and genotype
- Fetal period: month 3 to birth
Related conditions
- Hearing loss (conductive and sensorineural, including sudden hearing loss)
- Neonatal jaundice
- Tuberculosis
In Pharmacology
Educational content on embryonic development; not a guide to prenatal diagnosis or to medicines in pregnancy and no substitute for a health professional's advice. No doses are given.
Sources: Teratogenic Medications (StatPearls Publishing (NCBI Bookshelf), 2024); Langman's Medical Embryology, 13th ed., ch. 9: Birth Defects and Prenatal Diagnosis (Wolters Kluwer, 2015).
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Representative model, for educational purposes only.