Two groups of women with preterm labor will be included. One will receive magnesium sulfate for neuroprotection and the other will receive placebo. Fetal middle cerebral artery Doppler indices will be measured before and after intake of either magnesium sulfate or placebo to find if any significant changes occur in fetal cerebral blood flow.

The study will include women with preterm labor with gestational age less than 32 weeks. women will be randomized to receive either magnesium sulfate (loading dose 6 g over 20 minutes followed by maintenance dose of 1 g/hour for 24 hours), or placebo in the form of sodium chloride solution 0.9% over 24 hours. Fetal middle cerebral artery Doppler indices [Peak systolic velocity (PSV), Pulsatility index (PI), and resistance index (RI)] will be recorded before and after treatment in both groups. Results of Doppler indices will be compared between both groups and before and after intake of magnesium sulfate to find out if middle cerebral artery Doppler of the fetus can explain the mechanism behind the use of magnesium sulfate for fetal neuroprotection in preterm births.

Inclusion Criteria:

• pregnant women with preterm labor
• gestational age less than 32 weeks
• singleton pregnancy

Exclusion Criteria:

• contraindication or hypersensitivity to magnesium
• preeclampsia
• multiple pregnancy
• intake of magnesium sulfate in this pregnancy before