To a point, but there are clues:

马 is mǎ, meaning horse. It's a picture of a horse, with 3000 years of adaptation.

女 means woman / female. It's a picture of a woman.

Put them together and 妈 means "the female thing that sounds like mǎ", which is mā (a different tone), meaning mother.

(I'm very much a beginner, but my teacher claims ~70% of characters follow this pattern.)