Women were warned Wednesday that their risk of blood clots in the legs and lungs may be higher if they use the birth-control patch instead of the pill.

The Food and Drug Administration said it updated the label on the Ortho Evra birth-control patch to reflect the results of one study that found women using the patch faced twice the risk of clots than did women on the pill. However, a second study found no difference in risk between the two forms of birth control.