No Link Found Between Beta Blockers, Fetal Heart Problems: Study

Infants born to women using beta blocker drugs during pregnancy do not appear to face a higher risk of having heart problems in utero, according to the findings of new research. 

In findings published this month in the medical journal JAMA Internal Medicine, researchers with Kaiser Permanente in California indicate that initial data from a new study suggested a connection between the drugs and fetal heart problems. However, after adjusting for other factors, they dismissed the likelihood of a connection.

Beta blockers are the most commonly used class of medication to treat cardiac conditions during pregnancy, which are often used to manage arrhythmias and prevent a second heart attack after a first. Beta blockers are also commonly used during pregnancy to treat hypertension, or high blood pressure.

Researchers noted there is little published evidence to support the safety of these drugs during pregnancy, because beta blockers can cross the placenta and potentially cause changes to the fetus.

In a recent meta-analysis conducted, an association between beta blocker exposure and fetal congenital cardiovascular defects was found. So researchers set out to test the beta blocker fetal heart risks in a new retrospective population-based study.

The study involved nearly 400,000 births in the Kaiser Permanente Southern California Region from January 1, 2003, to December 31, 2014, using pharmacy dispensing records to identify women exposed to beta blockers during pregnancy. Researchers also used electronic medical records to identify fetal congenital anomalies and California birth certificates to identify fetal birth weights.

More than 4,800 women were exposed to beta blockers during the study; about 2,600 during the first trimester. The four most commonly prescribed beta blockers used during the study were drugs like Lopressor, Normodyne, Tenormin, and InnoPran XL.

Researchers said they found an association with “significantly increased odds” of fetal congenital cardiac anomalies among infants whose mother used beta blockers. However, after adjusting for other factors, like mother’s age, body mass index and other health problems, the association between the two appeared to vanish.

Pregnant women using beta blockers more commonly experienced other health concerns, such as hypertension, preeclampsia, diabetes, heart failure and history of arrhythmia, the researchers noted.

The findings contradict other studies, which have pointed to beta blockers causing bradycardia and hypoglycemia in infants.

The study did find a link between younger gestational age, as infants born to mothers who took beta blocker were often born at 37 weeks, compared to 39 weeks for those who didn’t take the drugs.

Researchers said other maternal health problems seem to explain the increased risk of fetal heart abnormalities, not the use of beta blocker drugs during pregnancy. The findings don’t definitively rule out the risk of fetal heart defects linked to beta blocker use, but the researchers concluded that it does show this is not a common occurrence.