Magnesium sulphate and fetal neuroprotection – when, how, why and why not?

Preterm delivery is strongly associated with neurological impairments, such as cerebral palsy (CP), motor dysfunction, blindness, developmental delay and intellectual impairment. Antenatal administration of magnesium sulfate (MgSO4) has become a valuable approach of the neuroprotective strategy for preterm births. MgSO4 can prevent excitotoxicity via N-methyl-D-aspartic acid (NMDA) receptor antagonistic action and has an anti-inflammatory effect. There is still no international consensus on the dosage, time of administration and the need to repeat MgSO4 treatment. However, most studies report benefits for ≤31+6 weeks of gestation (GW) and imminent preterm birth, defined as active labor with ≥4 cm cervical dilation with either failure or contraindication to tocolysis, ≥4 cm dilatation with documented progressive change in cervical dilation, preterm pre-labor rupture of membranes with active labor, and for planned delivery for fetal or maternal indications. MgSO4 is recommended in a loading dose of 4 g intravenously (i.v.) for 30 minutes, followed by a 1 g/hour i.v. maintenance infusion for maximum 24 hours. It has been shown a significantly reduced rate of moderate and severe CP for the premature receiving MgSO4, but also a lower rate of motor dysfunction and a lower systemic vascular resistance and higher myocardial function in preterm infants born before 29 WG. One the other hand, several side effects have been reported and should be closely monitored. Maternal side effects include hypotension, tachycardia, respiratory depression, drowsiness, headache and muscle weakness. One trial reported a higher incidence of spontaneous intestinal perforation among extremely low birth weight infants. In conclusion, antenatal MgSO4 administration is a first step in preventing neurological damage, but further studies are mandatory to standardize its use. [ABSTRACT FROM AUTHOR]