Carol Fishman Cohen was 30 and on maternity leave from Drexel Burnham Lambert when the investment banking firm imploded in February 1990. A Harvard Business School grad in the Boston office?s corporate finance group, she didn?t agonize about leaving her high-powered job. She picked up part-time special project work off and on. Soon she had another baby, and then another and another. Married to a lawyer, she spent five years working part-time and six years caring for her kids full-time.