January 9, 2015 — After evaluating about a dozen studies, the U.S. Food and Drug Administration (FDA) has found inconclusive evidence linking birth defects to the use of prescription and over-the-counter painkillers during pregnancy.
The FDA evaluated studies linking non-steroidal anti-inflammatory drugs (NSAIDs) with miscarriage in the first half of pregnancy, opioids and neural tube defects, and acetaminophen with attention-deficit hyperactivity disorder (ADHD).
According to the Safety Announcement:
“We found all of the studies we reviewed to have potential limitations in their designs; sometimes the accumulated studies on a topic contained conflicting results that prevented us from drawing reliable conclusions.”
The FDA specifically recommended against using NSAIDs in the third trimester of pregnancy because they can cause a blood vessel in the fetus to close prematurely. Drugs in the NSAID class include ibuprofen, naproxen (Aleve), diclofenac, and celecoxib.
NSAIDs and Miscarriage
The FDA looked at five studies involving miscarriage before the 20th week of pregnancy. Three studies involving 100,000 women reported a 7-fold increased risk of miscarriage, but there were serious methodological problems. For example, the researchers didn’t look at why women were taking the NSAID — some women may have been using the drugs to treat symptoms of miscarriage (i.e., cramping).
Opioids and Neural Tube Defects
Two studies used interviews to gather data on 28,000 women who used opioids during pregnancy; both studies found at least 2-fold increased risk of neural tube defects compared to mothers who did not take opioids. The FDA was concerned about the limitations of using interviews to gather data. Furthermore, because neural tube defects only occur in 4-6 per 10,000 births, even a doubled increased risk is numerically small.
Acetaminophen and ADHD
The FDA evaluated a study linking the use of acetaminophen during pregnancy with ADHD in children. Women who used acetaminophen were 13% more likely to report ADHD-like behavior, and 37% more likely to have a child diagnosed with hyperkinetic disorder (HKD). However, the FDA said the studies were inconclusive due to methodological limitations that made the findings “difficult to interpret.”