A woman in preterm labor at 30 weeks of gestation receives two 12-mg doses of betamethasone intramuscularly. The purpose of this pharmacologic treatment is to:
a. Stimulate fetal surfactant production.
b. Reduce maternal and fetal tachycardia associated with ritodrine administration.
c. Suppress uterine contractions.
d. Maintain adequate maternal respiratory effort and ventilation during magnesium sulfate therapy.