Mandy Moore is happily pregnant but dealing with a frustrating issue as a result.

The This Is Us star is eagerly awaiting the birth of her third child with her husband, Taylor Goldsmith . But she recently announced that she has been diagnosed with melasma , a condition that leaves brown or blue-gray spots on the skin.

Pregnancy melasma is the pits, she wrote in a since-expired Instagram Story, per E! News. The accompanying photo reportedly showed Moore lying down and rubbing her temple with a Lyma Laser , an at-home skin care device.

Melasma is a common condition but affects women far more often than men, according to the Mayo Clinic . The patches of color pigmentation, which usually appear on the face, are often triggered by sun exposure or hormonal changes due to pregnancy.

The condition runs in families, and recent research shows that the blue light from computer screens and other electronic devices can worsen the disorder. Treatment using intense pulses of light purportedly works to combat it.

Moore shares two sons , 3-year-old Augustus and 19-month-old Oscar, with her husband. She announced her third pregnancy in May, and told People in June that this time is different mainly because shes regularly chasing two wild toddlers around.

Shes since learned, meanwhile, that even a good pregnancy phase can change on a dime.