Botulinum Toxin in Pregnancy

The aging of human skin is a natural process described by two main processes - intrinsic and extrinsic. Intrinsic aging depends on one’s own genetics and the natural weakening of protein networks in the skin that occur slowly as we get older. Extrinsic aging describes our skin’s reaction to harsh environmental factors such as ultraviolet radiation amongst others.^[1] 

Both of these processes contribute to the inevitable outcome of aging skin - wrinkles, fine lines, and a less youthful appearance. For generations, cosmetic specialists have sought remedies to reduce the appearance of these changes.

One of the most effective treatments for reducing wrinkles and fines lines is botulinum toxin. Interestingly, this substance was first discovered to be produced by one of nature’s most unseemly creatures—the bacterium, Clostridium botulinum! This article will provide an overview of what botulinum toxin is, how it works, and its controversial safety of use during pregnancy. 

What Is Botulinum Toxin? 

Botulinum toxin is a substance that is naturally produced by a bacterium found in nature. There are eight different subtypes of the toxin that range from A-G, but only A and B are used for medical and cosmetic purposes. The difference between A and B toxin is that the effects of A last longer, but the effects of B toxin occur faster.^[2]

How Does Botulinum Toxin Work?

The cosmetic use of this substance was actually first discovered by an ophthalmologist who injected a small amount in the forehead area of his receptionist who had been complaining of a frown line. Amazingly, over the next several days, the line began to fade. 

Botulinum toxin works by essentially paralyzing the muscles in our body responsible for movement, called skeletal muscles. When administered in small, controlled amounts, it can paralyze small active facial muscles that are responsible for creating frown lines and other undesired facial lines.^[3] When using botulinum toxin A (the most commonly marketed form of the toxin), the effects of the injection usually take approximately 3-10 days to start working after the injections.^[1] The effects of toxin and wrinkle reduction can last for up to 3 months, at which time another round of toxin is usually needed to sustain the cosmetic benefits.^[4]

What Can Botulinum Toxin Do?

The short answer is a number of things. It has been used for disorders of muscular spasms for years. It has also been used to treat everything from migraines to overactive bladder disorders. From a cosmetic perspective, botulinum toxin is only FDA approved for the treatment of crow’s feet and improvement of glabellar lines (the area between the eyebrows). However, it has been used off-label for a number of cosmetic procedures including shaping and lifting the eyebrows, defining the jawline, treating circular neck bands, and many others.^[5]

Safety in Pregnancy

The most common general side effects with the use of botulinum toxin are headaches, swelling, and bruising. Other less likely side effects include eyelid drooping and unwanted weakening of other facial muscles due to the spread of the toxin. Injection site reactions and allergic reactions which cause rashes can also occur.^[6]

The safety of botulinum toxin use during pregnancy has not been tested in clinical trials. The concern with use would be the possibility that the toxin crosses the placental barrier. However, current data suggests (but does not confirm) that the size of the toxin molecule makes it unlikely for it to cross the barrier. Furthermore, it is unlikely that the toxin reaches high concentrations in the rest of the body when injected locally in small amounts, as with cosmetic botulinum toxin procedures.^[7]

There have been many case reports of the toxin being used inadvertently in pregnant women for various medical conditions. Two cases reported the use of the toxin in the esophagus in the first and third trimesters respectively. In neither case was there any harm observed to the fetuses. Both women had healthy, successful deliveries.^[8,9] There have been other cases in which women have received toxin for migraine headaches and muscular spasm of the neck. Generally, no adverse events thought to be related to the toxin were noted.^[10]

There is concern that high doses (>600 units) of the toxin may lead to whole-body weakness, but doses used in cosmetic procedures are usually less than 100 units.^[11]   

No definite recommendations can be made at this time on the safety of botulinum toxin during pregnancy despite several individual reports of safe use. Some experts recommend waiting until after pregnancy to proceed with treatment. Botulinum toxin A has officially been labeled by the FDA as pregnancy category C, meaning there is a lack of studies in pregnant women, but animal studies may have described harm to the fetus. The toxin is lactation category L3, meaning there are no controlled studies in breastfeeding women and potential unknown risks to the baby might exist.