Cohen just wrote an article in the Philadelphia Inquirer about checking prescriptions and questioning misspelled names.
Silva is being carefully watched by doctors, who say she could miscarry, carry to term a baby with severe birth defects or have a perfectly normal child.
The reason methtrexate works so well as a cancer and inflammatory arthritis medicine is because it attacks rapidly reproducing cells -- precisely why it is so dangerous in pregnancy.
"The effect on the baby is probably the biggest concern, because it's a drug that is used in high doses to induce abortion," said Marcel Casavant, chief of pharmacology and toxology at Nationwide Children's Hospital in Columbus, Ohio.
But even at lower doses, the drug can cause a "collection of abnormalities" to the babies exposed during pregnancy, including birth defects like throat problems, facial abnormalities and neurological problems.
Silva's unborn child had "50-50 chance" of having problems, according to Casavant. "The good news is that a lot of other women have been exposed inadvertently to the drug during pregnancy and not every baby gets a birth defect. They end up just perfectly fine."
Some of the potential abnormalities will show up on a later sonogram, but other developmental problems might not be detected until the baby is born, he said.
"The standard advice for anyone is to talk with your doctor about what your prescription is and what it is for," said Casavant. "Your pharmacist is supposed to offer counseling and it's a good idea to get it, especially if something doesn't look quite right. Double check, before you take it."
And if a patient thinks they have taken the wrong medicine, call the poison control center right away at 800-222-1222.
As for mistakes involving methotrexate during pregnancy, contact The Otis Rheumatoid Arthritis Study, which has the latest information on the drug.