A baby’s teeth are not visible at birth, but already exist underneath 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.

There are certain steps you can take to ensure your baby is born with healthy teeth. Diet is key, and there are certain nutrients that are especially important for prenatal tooth development:

• Calcium

Calcium is the main component of teeth. If there is not enough calcium in your diet to support fetal development, your body will actually take this mineral from your bones and use it to meet your developing baby's needs. Good for your baby, not so good for you. The best sources of dietary calcium are dairy foods such as milk, cheese, and yogurt. It can also be found in broccoli and kale.

• Phosphorous

Phosphorus helps balance the amount of calcium in our bodies, and accounts for the hardness of teeth. The richest sources of phosphorus come from dairy, red meat, poultry, seafood, legumes, and nuts.

• Vitamin D

Vitamin D helps our bodies absorb and use calcium. It is found in fish like salmon and tuna. Sometimes it is added to beverages, like orange juice and milk. It is also produced in the body naturally when skin is directly exposed to sunlight. Concerns about the negative effects of sun exposure may prevent you from getting all the vitamin D your body requires this way, so you may be advised to take a supplement.

• Protein

Protein is responsible for building, maintaining, and replacing the body’s tissues. It is the action of a single protein that causes calcium-phosphate crystals to form tooth enamel rather than bone. Meats and dairy products are the most protein-rich. It is possible to get all the different proteins your body requires with a vegetarian diet, but you will need to pay closer attention to what combinations of foods will provide all the essential amino acids.

It’s also important to know that certain antibiotics and supplements should be avoided during pregnancy. 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. Before getting a new prescription, make sure to discuss your pregnancy with your healthcare provider.