The Food and Drug Administration yesterday said it will require

all over-the-counter aspirin products to carry a warning that

the drug should not be used by women in the last three months of pregnancy unless directed by a physician.

The agency said the warning on labels is being required because aspirin can affect fetal circulation and uterine contraction, which can harm the baby and cause problems during delivery.

Manufacturers have one year to add the stronger warning to all oral and rectal over-the-counter products containing aspirin, the FDA said.

The warning must read: "It is especially important not to use aspirin during the last three months of pregnancy unless specifically directed to do so by a doctor, because it may cause problems in the newborn child or complications during delivery."

Aspirin products now carry a general warning that says:

"As with any drug, if you are pregnant or nursing a baby, seek the advice of a health professional before using this product."

An advisory panel of medical experts had recommended the stronger warning.

A similar, third-trimester pregnancy warning already is required on nonprescription products containing the pain-reliever ibupro- fen.

The regulation is to be pub- lished Thursday in the Federal Register.