A federal spending law has college students concerned--about its effects on the cost of their birth control. The health center at Indiana University has doubled the costs of many common contraceptives--and students in Ohio, Nebraska, and Wisconsin are also worried. University health centers had been able to sell contraceptives at lower cost by taking advantage of drug makers' group discounts. A federal spending bill passed last February changes the rules on who can get discounts. The president of the American College Health Association acknowledged the concern in a Jan. 5 letter, promising to address it when the group's board of directors visits Capitol Hill next month.