Women make up only 28% of the workforce in STEM fields and the gender gaps are high in fields like computer science and engineering. Only 21% of engineering majors and 19% of computer science majors have women. This is because of gender stereotypes, fewer female role-models, and the male-dominant culture where these fields aren't supported because fewer females study it. 

Source: https://www.aauw.org/resources/research/the-stem-gap/