What is Preterm Labor?
Preterm labor is defined as regular contractions resulting in a cervical change before 37 weeks of gestation. If labor proceeds and a baby is delivered, the baby is at greater risk of developing birth complications and injuries than a baby born at term. During labor and delivery, the fragile bodies of premature infants are subject to immense stress, and if labor is mismanaged they are susceptible to injuries like hypoxic-ischemic encephalopathy (HIE) and cerebral palsy. Luckily, there are certain precautions (like magnesium sulfate use) that medical professionals can take to treat preterm labor by slowing the labor process.
How Can Magnesium Sulfate Help with Preterm Labor?
Magnesium sulfate, an inorganic salt, is one of the most common treatments for preterm labor. Magnesium sulfate is a tocolytic, a medication used to suppress premature labor. Tocolytics like magnesium sulfate work by slowing or inhibiting contractions in order to delay premature birth. The medication works by lowering calcium levels in the uterine muscles, allowing for muscle relaxation.
Magnesium sulfate can prevent or delay preterm birth for several days or longer. While this amount of time may seem minimal, it may give medical professionals time to prepare the baby for birth by administering prenatal steroids like betamethasone, which help the baby’s lungs become ready for extra-uterine life and act as a neuroprotector.
Magnesium sulfate is administered through an IV, at a dose of around 6 grams, over a span of 15 to 30 minutes. Subsequently, a maintenance dose of about 2 grams is given each hour.
Is Magnesium Sulfate Safe for All Pregnant Women?
While magnesium sulfate administration is known to be safe in most pregnant women, it should not be given under certain circumstances. Women who have one or more of the following conditions should not receive magnesium sulfate for preterm labor:
- Myasthenia gravis
- Myocardial compromise
- Cardiac conduction defects
- Impaired renal (kidney) function
- Preventing Premature Birth
- Cervical Cerclage
- Magnesium Sulfate for Neuroprotection
Hyagriv N Simhan & Steve Caritis, “Inhibition of acute preterm labor,” UpToDate (2017): https://www.uptodate.com/contents/inhibition-of-acute-preterm-labor/.