CONCORD, N.H. (AP) - A congresswoman from New Hampshire asked the U.S. government Tuesday to clarify how families can obtain coverage under the federal health insurance law when children are eligible for Medicaid but their parents are not. Parents in New Hampshire, California and Florida have been surprised to learn that children who qualify for Medicaid can't be covered under subsidized family plans purchased through the federal online markets, The Associated Press reported this week. Some children are going without coverage temporarily while their eligibility is determined. Others are stuck with no options because they applied for Medicaid and were rejected, but can't be added to their parents' plans. In response to the AP report, Democratic U.S. Rep. Carol Shea-Porter wrote to the Centers for Medicare and Medicaid Services asking it to issue guidance to insurers, consumer assisters and the public by Monday. Consumers deserve answers from CMS. My constituents should have had easy access to guidance about this situation long before enrollment began in October," she wrote. Now it is late January, the enrollment period for marketplace health insurance is more than half over, and coverage has already begun for many families. The delay in providing guidance is troubling. Among other questions, she asked CMS to explain what options exist for families when a child's Medicaid eligibility determination is delayed or unsuccessful and what it can do to help children who have been deemed ineligible for Medicaid to be added retroactively to a family's subsidized plan. Individuals shopping for insurance through the new online markets are referred to state Medicaid offices if they might qualify for the safety-net program for the poor and disabled. But the situation is more complicated for families, because in some states parents must have significantly lower incomes to gain Medicaid coverage for themselves than they would to get coverage for just their children. The problems some parents have faced came up at a recent meeting of New Hampshire's Health Exchange Advisory Board, where a regional manager for CMS acknowledged the problem and said the agency is working on it. But the office declined to answer more detailed questions later about how the system is supposed to work and what problems have emerged.