During my last pregnancy, I had frequent migraine headaches and wondered which medications were safe to take.

With rules about pregnancy medications constantly changing, it can feel overwhelming to know what to do when feeling sick. It usually comes down to weighing the benefits for a mother with a health condition — even one as simple as a headache — with potential risks to her developing baby.

The problem is, scientists can’t ethically perform drug testing on a pregnant woman. It’s not accurate to say a medication is 100 percent safe simply because it’s never been studied or tested.

In the past, medications were assigned to categories of safety by risk level, from A to X. Category A was the safest category of drugs to take. Category X were to be never used during pregnancy.

But as of 2015, the U.S. Food and Drug Administration (FDA) has moved to a new labeling system for drugs.

Instead of lettered categories, the FDA’s new labeling system for medications is much simpler and lists only three categories:

Pregnancy

Pregnancy includes labor and deliver. This label contains all existing and updated information in a new pregnancy exposure registry for available drugs.

Before the new labeling system, a pregnancy exposure registry didn’t exist. But now it’s required. It’s optional for women to enroll in the registry so doctors can learn more about how drugs affect women and their babies during pregnancy.

The information on the registry includes potential risks and side effects of taking a medication during pregnancy, labor, and delivery.

Lactation

Lactation includes women who are breastfeeding. This label informs about levels of drugs that will be present in breast milk and potential effects on a breastfeeding infant.

Females and males of reproductive potential

This label covers anyone with the potential of having children. It tells doctors or other medical staff when pregnancy testing, contraception recommendations, and information about infertility is necessary.

One important note about the new labeling system is that it doesn’t affect over-the-counter (OTC) medications at all. It’s for prescription-only drugs.

The pregnancy exposure registry is new. Information is still being collected about different kinds of medication and their possible effects on pregnant and breastfeeding individuals.

But there are some guidelines for specific medications that people should avoid during their pregnancies. With these drugs, there’s a stronger link to an adverse reaction. Doctors warn pregnant women not to take them.

Below is a sampling of medications pregnant women should avoid. Many of them are antibiotics.

Chloramphenicol (Chloromycetin) is an antibiotic. It’s usually given as an injection. This drug can cause serious blood disorders and gray baby syndrome.

Ciprofloxacin (Cipro) and levofloxacin (Levaquin) are types of antibiotics. These drugs could cause problems with the baby’s muscle and skeletal growth as well as joint pain and potential nerve damage in the mother.

Primaquine is a drug that’s used to treat malaria. There isn’t a lot of data in humans for taking this drug during pregnancy, but animal studies suggest it’s harmful to developing fetuses. It can damage blood cells in a fetus.

Sulfonamides are a group antibiotic medications. The majority of these types of drugs are used to kill germs and treat bacterial infections. They can cause jaundice in newborns.

Trimethoprim (Primsol) is a type of antibiotic. When taken during pregnancy, this drug can cause neural tube defects. These affect brain development in a developing baby.

Codeine is a prescription drug used to relieve pain. The drug has the potential for becoming habit forming. It can lead to withdrawal symptoms in newborns.

High doses of this over-the-counter pain reliever can cause many serious problems, including:

  • miscarriage
  • delayed onset of labor
  • premature closing of the fetal ductus arteriosus
  • jaundice
  • hemorrhaging for both mother and baby
  • necrotizing enterocolitis
  • oligohydramnios
  • fetal kernicterus
  • abnormal vitamin K levels

Warfarin is a blood thinner. It’s used to break up blood clots. It can cause birth defects and is avoided during pregnancy unless the risk of a blood clot is more dangerous than the risk of harm to the baby.

Clonazepam (Klonopin) is used to prevent seizures and panic disorders. The medication is sometimes prescribed to treat anxiety or panic attacks. It’s known to pass into breast milk.

This is a common medication used for anxiety or other mental health disorders. It can cause birth defects or life-threatening withdrawal symptoms in a baby after birth.

If you’re not sure whether or not a medication is safe to take during pregnancy, ask your doctor. Also ask about updated studies, as medication categories can change with new research.


Chaunie Brusie, BSN, is a registered nurse in labor and delivery, critical care, and long-term care nursing. She lives in Michigan with her husband and four young children and is the author of “Tiny Blue Lines.”