A human fetus begins to develop teeth after just 28 days in utero, although the teeth don't emerge until six to 12 months after the baby has been born. The primary teeth, or baby teeth, start forming during the sixth to eighth weeks of pregnancy, followed by the formation of the permanent teeth starting in the 20th week. Both the primary and permanent teeth are soft until about the 14th week in utero, when they begin to mineralize and get their hard enamel layer.
More facts about teeth:
- The timing of the formation of the teeth in utero is extremely important. If the teeth don't start forming between the third and 20th weeks, they won't form at all.
- Lower teeth typically come in before upper teeth, and girls tend to get their teeth before boys.
- Rarely, a child can be born with a tooth already showing or have a tooth come in soon after birth. When this occurs, the tooth often has to be removed because it can damage the mother's breasts during feeding.