The U.S. Food and Drug Administration (FDA) on Wednesday proposed new changes to labels on drugs prescribed to pregnant and breast-feeding women.

If enacted, the new system would replace a 30-year-old system for classifying drugs in favor of labels that provide more detailed information to doctors prescribing the drugs.

According to doctors, the current system that relies on letter designations to describe the risks of a drug when taken during pregnancy or breast-feeding is confusing and incomplete.

Under the current system, prescription drugs carry a code in the fine print of their labels where Category A means it's deemed safe for pregnancy; Category X means it's known to harm human fetuses. A drug given the remaining B, C or D codes have varying levels of evidence one way or the other.

The new labels would include three new sections. "Fetal Risk Summary" would describe the known effects of a drug on a fetus. "Clinical Considerations " would include information about effects associated with a drug taken before a woman is aware of her pregnancy. "Data" would describe information available about the drug's use in humans and animals studies.

The new system would also keep in mind women with pre-existing medical conditions, such as asthma or high blood pressure, who may need to use prescription drugs during the period.

The newly proposed changes still must undergo public review.