Role models and encouragement can make a big difference when it comes to education program and career choices. Currently, less than 25% of STEM (Science, Technology, Engineering, and Math) in the US are held by women.
Recent research (*) suggests that boys and girls have similar psychological traits and cognitive abilities, thus gender is not the determining factor for careers in STEM.
One contributor could be repeated (but often concealed) encouragements that reinforce gender stereotypes (see video below). Women need more role models, opportunities to experience, and encouragement towards careers in STEM.
(*) Hyde, J. S., & Linn, M. C. (2006). Gender similarities in mathematics and science. Science, 314(5799), 599-600