5 weeks pregnant. usg shows 3 uterine fibroids:anterior wall subserosal (7.5*6.0mm), posterior wall (17.6*11.2mm) and fundal region (22.7*20.1). harmful?

Probably not: The vast majority of women with small fibroids such as these have normal fertility and uncomplicated pregnancies. Submucosal fibroids, especially if large, may be a cause of miscarriages.

Not harmful: These are very small fibroids if your measurements are correct (7.5-20 mm). They should have no effect on the pregnancy. If they grow larger in the future they may have to be addressed.