Effect of Terbutaline on a Fetus

Terbutaline, also known as Brethine, is one of several tocolytic drugs used to treat premature labor. Tocolytics are medications that slow down or halt contractions of the uterus. While there are several different tocolytic drugs available for use today, terbutaline is the most commonly prescribed because it is available as an injectable or IV for hospital use as well as a pill that can be continued by patients at home.

Positive Effects of Terbutaline on the Fetus

Terbutaline positively affects the fetus by relaxing the smooth muscle of the mother's uterus, delaying delivery for several days. During this time, doctors may opt to treat with steroids, which have been proven to reduce the risk of lung problems for premature babies, improving their chances of survival by as much as 40 percent. Steroid therapy works fast with improvements in infant lung function seen within 48 hours.

Mild Side Effects

As with all types of drug therapy during pregnancy, the use of terbutaline can pose risks. Generally considered safe, doctors worldwide consider terbutaline a standard treatment for premature labor, however, it is not approved by the FDA for this purpose and is classified as an asthma drug. There are those in the medical community who doubt terbutaline's effectiveness and safety, especially when given over longer periods of time.

The most common side effects of terbutaline on a fetus include increased heartbeat, increased blood insulin levels, abnormal blood sugar levels (either too high or too low), jaundice and low blood pressure. Fortunately, these side effects have a low incidence of long-term damage on the newborn and are typically easy to treat.

Severe Fetal Side Effects

Unfortunately, terbutaline treatment can also have some severe fetal side effects, such as:

  • enlarged heart
  • congenital heart defects
  • brain bleeds
  • bleeding into the heart

While some congenital heart defects are considered easy to fix, others can require several complicated surgeries and long-term medical treatment. Brain bleeds (also known as intracranial hemorrhage) can lead to devastating side effects such as developmental/learning disabilities, cerebral palsy and vision problems. As with all medical treatments, terbutaline therapy can potentially lead to fetal demise although situations in which fetal death was directly blamed on terbutaline have not been widely reported.

A Possible Link to Autism

A study conducted at Duke University by Theodore Slotkin, Colleen Oliver and Frederic Seidler in 2005 revealed that exposure to terbutaline while in the womb can have a negative effect on brain development. Terbutaline causes the neuro-transmitters in the fetal brain to become over stimulated. In addition, researchers noted an abnormal vulnerability to everyday pollutants and chemicals in children whose mothers received terbutaline, which could also be a factor in the development of autism and other cognitive disorders 2.


When considering treating preterm labor with terbutaline, medical professionals must consider both the positive and negative effects of the drug on the fetus 1. Pregnant women experiencing preterm labor should discuss any concerns they have about terbutaline therapy with their doctors and work together to decide if the benefits outweigh the risks 1. Many doctors feel that use of terbutaline may have little value past the initial 48 hour period and can lead to a higher incidence of negative outcomes.