Fetal Neuroprotection by Magnesium Sulfate

Introduction

Preterm babies are at higher risk of dying in the early weeks of life than babies born at term, and those preterm babies who survive are affected by cerebral palsy or physical disabilities. Cerebral palsy is a disorder where the ability to move the arms and legs is typically reduced. So, magnesium is an essential element that helps in normal body function. In addition, it helps to decrease the damage to the preterm baby and their brains. However, mothers have to deal with side effects like flushing, nausea, vomiting, headaches, or sweating.

What Are the Uses of Magnesium Sulfate in the Body?

The usage of magnesium sulfate includes the following:

• Magnesium contributes to physiological processes like storage, metabolism, and energy utilization.

• It is essential in protein, DNA (deoxyribonucleic acid), and RNA (ribonucleic acid) synthesis.

• It helps produce ATP (adenosine triphosphate) and in cell membrane stabilization.

• It acts as a calcium channel blocker and modulates the sodium and potassium flux.

• It works in the brain to bind chelators such as ATP and to work as a cofactor for enzymatic reactions.

• But in the central nervous system, it works as a non-competitive blocker of glutamate receptors NMDA (N-methyl-D-aspartate).

What Are the Indications for Magnesium Sulfate for Fetal Neuroprotection?

Indications are:

• Women in preterm labor (pregnant women with regular contractions accompanied by the cervical change) and patients with single or twin cases who are expected to deliver within 24 hours.

• Women with premature rupture of membranes.

What Are the Contraindications of Magnesium Sulfate?

Contraindications of magnesium sulfate are:

• Women with a short cervix are not delivering within 24 hours.

• Women with preterm contractions without cervix changes.

• Women who have not delivered within 12 hours of admission for preterm labor.

• Patients who are dealing with conditions like myasthenia gravis (autoimmune disorder with weakness in muscles), muscular dystrophy (a disease with progressive weakness and loss of muscle mass), myocardial infarctions (disease of the heart due to its blockage), and impaired renal functions because it can cause dangerous side effects on magnesium sulfate usage.

Why Is Magnesium Sulfate Used for Neuroprotection?

Babies, when born, have fragile brains and can get brain injuries as they are at high risk of developing hypoxic ischemia, encephalopathy, and cerebral palsy. Here the use of magnesium sulfate reduces the risk of preterm birth-associated brain injuries in two ways.

1. Antenatal use of magnesium sulfate is used to suppress premature labor pains and delay preterm birth; all such provides the doctor time to deliver antenatal steroids that helps overcome the birth injuries in the babies.

2. Using magnesium sulfate provides direct neuroprotective effects on the baby's brain.

The studies have provided that using magnesium sulfate has prevented the babies from cerebral palsy, bleeding into the fluid-filled areas surrounding the brain (intraventricular hemorrhage), and injury to the white matter causing fluid-filled in the brain (periventricular leukomalacia).

How Does Magnesium Sulfate Protect Baby’s Brain?

The use of magnesium sulfate has provided neuroprotection for the fetus. Although the exact information about the usage in-utero is not present, the hypothesis of the use of magnesium sulfate usage in-utero is as follows:

• Magnesium sulfate stabilizes blood pressure and normalizes cerebral blood flow.

• It also stabilizes the neuronal membrane and blocks the excitatory neurotransmitters.

• Magnesium also protects the baby from oxidative injuries.

• It also protects against inflammatory injury.

What Is the Mechanism of Action for the Neuroprotective Effects of Magnesium Sulfate?

Several mechanisms affect preterm brain injuries.

• As a non-competitive NMDA receptor antagonist, magnesium sulfate prevents calcium-induced injuries.

• Magnesium limits the use of calcium influx, further decreasing apoptosis's activation.

• It has an anti-inflammatory property that reduces oxidative stress and reduces pro-inflammatory cytokines.

How Is Magnesium Sulfate Administered in Pregnant Women?

The magnesium sulfates are administered to pregnant women who are likely at risk of developing preterm labor and birth or to women who are expected to deliver the baby within 24 hours. They include premature ruptures of membranes or patients who are in preterm birth without ruptures. The use of magnesium in those women is between 24 to 32 weeks gestation. The dose of magnesium sulfate contains four grams of loading dose given intravenously followed by a one-gram maintenance dose given every 24 hours until the baby is not born.

What Is the Dosing Regimen for Magnesium Sulfate?

Magnesium sulfate is likely administered within 24 hours of preterm birth. There are three dosing regimens for it.

• Intravenous injection of 4 grams over 20 minutes followed by 1 gram per hour until delivery for 24 hours.

• An intravenous injection of 4 grams over 30 minutes or an intravenous bolus of 4 grams is given as a single dose.

• Intravenous 6 grams over 20 to 30 minutes, followed by intravenous maintenance injection of 2 grams per hour.

What Is the Procedure for Magnesium Sulfate Administration?

The procedure involves:

• An intravenous line is maintained for the saline solution.

• The catheter is inserted.

• External fetal monitoring is done before and during the time of infusion.

• A loading dose of 6 grams of magnesium sulfate over 20 minutes is prepared, followed by a 2 grams per hour dose for 12 hours or 4 grams of magnesium sulfate over 20 min, followed by 1 gram every hour.

• The infusion is stopped after 12 hours.

What Are the Side Effects of Magnesium Sulfate Usage?

There are side effects related to the mother. Some of the effects are:

• Maternal hypotension.

• Maternal tachycardia.

• Headaches.

• Sweating.

• Nausea.

• Vomiting.

Is Magnesium Sulfate Safe to Use in Pregnant Women and Their Babies?

Magnesium sulfate is safe for pregnant women and their babies, as its effects have been observed and studied. The effects of magnesium sulfate in mothers have side effects, but it is safe for usage.

Conclusion

Magnesium sulfate is used for neuroprotection in pregnant women to overcome any brain injuries that occur in preterm babies (babies delivered before the entire term of gestation). Preterm babies can develop cerebral palsy, blindness, or any physical disabilities. Magnesium sulfate administered to pregnant women before they deliver preterm babies causes a reduction in cerebral palsy. A dose of four grams is delivered to the woman who will deliver babies in 24 hours, followed by one gram after every hour is delivered. So it's completely safe to use magnesium sulfate on pregnant women.