What are the medical contraindications to tocolytics for the treatment of preterm labor?

Updated: May 04, 2021
  • Author: Michael G Ross, MD, MPH; Chief Editor: Carl V Smith, MD  more...
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Tocolytics should be used with considerable caution in pregnant patients with cardiac disease, especially those who require medication or have a history of congestive heart failure, cardiac surgery, significant pulmonary disease, renal failure, or maternal infection (ie, pneumonia, appendicitis, pyelonephritis). In these cases, it may be prudent to consult with an MFM specialist.

Specific tocolytic agents should not be used whenever known allergies exist. Indomethacin is contraindicated in the presence of aspirin-induced asthma, coagulopathy, or significant liver disease.

Magnesium sulfate should not be used in conjunction with select medications, such as calcium channel blockers, or when myasthenia gravis or neuromuscular disorders exist. In addition, the US Food and Drug Administration (FDA) has warned against extended magnesium sulfate injections in pregnancy. In 2013, the FDA issued a safety alert advising against the off-label administration of magnesium sulfate injections to pregnant women for more than 5-7 days as a means of stopping preterm labor, as this agent can lead to low calcium levels and bone abnormalities in the fetus. [26, 27, 28]

The warning was based in part on 18 case reports of skeletal abnormalities in infants whose mothers had received magnesium sulfate injections to stop preterm labor. In these cases, fetuses were exposed to the drug for nearly 10 weeks, on average, with neonates developing transient osteopenia and fractured bones. Epidemiologic evidence also indicates a connection between maternal administration of magnesium sulfate for more than 5-7 days and hypocalcemia and skeletal abnormalities in neonates. [26, 27, 28]


Beta-mimetics (eg, terbutaline) may be contraindicated in the presence of cardiac arrhythmia, valvular disease, and ischemic heart disease and may alter glucose homeostasis in patients with diabetes.

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