If you have a nanny or childcare is handled personally, so much the better. But a company that has on site childcare, or provides pretax dollars for childcare offers an incentive for working mothers, and generally has a mindset that appreciates the value that women can supply. This is a good place to start. Those that present flex hours, job sharing, and part-time professionals as options are doing that to allow their staff the ability to choose. This choice means that women can create a schedule with room in it to make the most of the family life.
Many corporations rate employee job satisfaction as a priority.
Companies that have women advancing through the ranks are companies that are generally open to the balancing needs that most women have. Unless all those women on the executive level have abandoned their families or are single, there should be many mothers in a company. This is a sign that the business encourages women to advance. While this sounds simple and almost mundane, it is actually essential. Ask anyone who commutes more than an hour each way to work and they will tell you that it kills their home time.