soccer mom

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun An American mother living in the suburbs whose time is often spent transporting her children from one athletic activity or event to another.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun Literally, a woman with school-age children, especially one who spends time transporting them between sporting activities.
• noun US A stereotype or demographic referring to women, typically middle-class, who are overly ambitious with their children’s success.