Pregnancy can cause changes in the pigmentation of the skin, including the pigmentation of moles. It is common for moles, especially those located on the face, nipples, genitals, armpits, or thighs, to become larger or darker when a woman is pregnant. Hormonal changes related to pregnancy may be responsible for the increase in pigmentation.
It is difficult for pregnant women to distinguish normal pregnancy-related changes in moles from those that may be indicative of the skin cancer melanoma. Pregnancy does not make it more likely that a woman will develop melanoma. However, there have been instances where melanomas occurring during pregnancy have not been detected promptly because the woman thought that they were normal pregnancy-related skin changes. With melanoma, as with many types of cancer, early detection improves the outcome of treatment, so it is important that melanomas be detected as quickly as possible.
A pregnant woman who notices a change in a mole should bring it to the attention of her doctor. If the mole looks in any way suspicious, she may need to have it examined by a dermatologist. It is safe for a woman to have a skin biopsy, the diagnostic test used to identify melanomas and other skin cancers, at any time during pregnancy. It is also possible to treat melanoma during pregnancy, but the fact that the woman is pregnant makes treatment more complicated.
The American Academy of Dermatology recommends that any pregnant woman who is at increased risk of developing melanoma because she has had a melanoma in the past, because members of her family have been diagnosed with melanoma, because she has many moles or atypical moles, or because she has other factors that increase her risk should inform her obstetrician so that this information can be taken into account at her regular prenatal office visits. Also, women who have a higher risk of developing melanoma should get their skin examined by a dermatologist during their pregnancies.