Your baby's teeth will not be visible at birth. But believe it or not, they already exist beneath the gums. Children's primary teeth begin forming at about the sixth week of pregnancy, and start mineralizing — building the bonelike inner tooth layer (called dentin) and the super-hard enamel layer that covers it — around the third or fourth month of pregnancy. So if you're pregnant, it's not too early to start thinking about how to make sure your child's teeth are as healthy as possible!
Like everything else having to do with your baby's physical development before birth, much depends on how well you take care of yourself. Developing teeth need certain nutrients to grow properly; if you don't get them through your diet, your baby won't receive them either. Likewise, you'll have to watch your intake of substances that could harm your teeth in utero, such as certain antibiotics. Here's a brief summary of what to seek and what to avoid.
Certain nutrients are particularly important for prenatal tooth development:
Seek Guidance on Dietary Supplementation & Medications
If you feel your diet is inadequate in some nutrients during your pregnancy, it's best to seek professional medical advice on what supplements you may need. While it's unlikely you will ever receive too much of any given nutrient from your diet, you can overdo certain vitamins and minerals in pill form (vitamin D and calcium, for example).
When you know you're pregnant (or if you may be pregnant), please share the news with all of your healthcare professionals who see you. That way, medications that should not be prescribed will be avoided at this time. For example, if you need antibiotics to combat an infection, some are much safer for developing babies than others. Tetracycline, for example, can permanently stain teeth in utero. Fluoride supplementation at this time is not recommended either, as there are too many unanswered questions about its use during pregnancy.