We Don’t Know Much About Meds for Moms

February 14, 2017

More research and regulations are needed to shine a light on how pregnancy affects the body’s ability to break down and absorb most medications.

As women have children later and later in life, the need to take medications during pregnancy is on the rise. Unfortunately, because very few studies have been conducted on how medications work in pregnant women, we’re really in the dark as to what kind of effects they have on both women and their fetuses. But new legislation aimed to address this lack of knowledge has finally been proposed.

Pregnant women are warned against eating or drinking many things—alcohol, caffeine, sushi, soft cheeses, to name a few—and when it comes to medication, similar precautions are taken. The problem is we actually have no idea how most medicines affect pregnant women or her fetus.

“I think it’s very important for anybody taking care of pregnant women on medication to understand that there are significant risks to not treating pregnant women,” says Maged Costantine, an Ob/Gyn and Associate Professor in the Department of Obstetrics and Gynecology at the University of Texas Medical Branch.

And women definitely take medicine while pregnant. One study reported that in 2008, more than 90 percent of pregnant women took at least one medication, prescription or over-the-counter, at some point during their pregnancy. And as the average age for first-time mothers is increasing, the need for medication is increasing both because they’re at greater risk for developing complications that need to be treated and because they’re already treating chronic age-related issues like hypertension or diabetes.

But women’s bodies change drastically during pregnancy and those changes affect the way the body responds to and breaks down medications. Blood volume and heart rate increase, movement through the gastrointestinal tract slows, the kidneys filter the blood faster, and enzymes in the liver that break down medications become more or less active depending on the enzyme.

“That’s just pure, natural pregnancy,” says Maisa Feghali, an Assistant Professor in the Department of Obstetrics, Gynecology, and Reproductive Sciences in the Magee-Women’s Hospital at the University of Pittsburgh Medical Center. “That happens to every single pregnant woman.”

“Most of these changes ultimately would affect how the body handles drugs during pregnancy,” says Costantine. The increase in blood volume can decrease the concentrations of proteins in the blood that bind to and effectively neutralize drugs. With less binding, more of the drug is available to have an effect. The slowed gastrointestinal system can give more time for medications to be absorbed into the bloodstream. And maybe most importantly, changes in kidney and liver activity can lead to medications being filtered out of the body faster.

“In other words, that means they have a very efficient elimination system for drugs and substances in their body,” says Shinya Ito, the Clinical Pharmacology and Toxicology Division Head at the Hospital for Sick Children in Toronto.

This mix of effects can have different results depending on the medication. For some drugs it might mean that they have a stronger effect even at the same dose. For others it could mean the exact opposite, at the same dose the drug is much less effective. But for most medications, we have no idea how they work in pregnant women because we’ve never studied it. And with such little information, some pregnant women choose to err on the side of caution, which could mean suffering through pain, discontinuing antidepressants, and putting themselves at risk of disease.

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