The Food and Drug Administration is telling aspirin makers to warn women not to take the popular pain killer during the last three months of pregnancy lest they risk prolonged labor and unnecessary bleeding.

Aspirin products already must carry the standard warning: "As with any drug, if you are pregnant or nursing a baby seek the advice of a health professional before using this product."This additional wording would be required under the FDA proposal issued Thursday: "IMPORTANT: Do not take this product during the last three months of pregnancy unless directed by a doctor. Aspirin taken near the time of delivery may cause bleeding problems in both mother and child."

A similar warning already is required for ibuprofen, the pain reliever used in such products as Advil and Nuprin.