There has not been sufficient testing done on the effects of using a bleach or peroxide gel while pregnant.  Until such studies have been done on a large scale, it might be best to err on the side of caution.  Manufacturers of teeth whitening products and teeth bleaching products generally recommend against using them during pregnancy for liability reasons.

There are several issues to be aware of regarding oral hygiene and pregnancy.  while you are pregnant your body experiences many hormonal fluctuations.  The changing levels of hormones in your body can affect your oral health as well as many other areas of health.  Specifically, these changing hormones make your gums more sensitive to plaque.  If you become pregnant while you already have gum disease, pregnancy can intensify it.  While you are pregnant, it is especially important to practice good oral hygiene.

Increased blood flow through the body will often make the gums swell.  This also increases your vulnerability to gum disease.  Additionally, during pregnancy most pregnant women have some bleeding of their gums, particularly while brushing or flossing.   You may also notice that your mouth produces more saliva during pregnancy.

When you visit your dentist you should inform her if you are pregnant or trying to become pregnant.  Dental x-rays may not be safe during pregnancy, and knowing you are trying to become pregnant can help in planning x-ray treatments. 

There are several steps you should follow while you are pregnant to insure good oral hygiene.  Brush thoroughly at least twice a day, preferably in the morning and before bed.  If possible, brush after every meal for at least five minutes at a time.  If you vomit, you should brush afterward to clean your teeth and mouth.  Use a good quality, soft-bristled toothbrush and toothpaste containing fluoride.  If you have a lot of sensitivity, try using toothpaste designed for sensitive teeth.  If you experience pain after brushing, use ice to sooth the pain and reduce swelling.

You should schedule a dental appointment immediately if:  Your gums bleed a lot or are painful, you experience breath that doesn’t go away, you lose a tooth or have pain in a tooth, or if you have a lump or growth in your mouth.  Decaying teeth and gum disease can lead to an infection which may complicate pregnancy. 

Can I bleach my teeth during pregnancy?