Final answer:
Glucocorticoids like betamethasone are used between 24 and 34 weeks of gestation to promote fetal lung maturity in cases of potential preterm birth, with administration generally happening before 34 weeks.
Step-by-step explanation:
Glucocorticoids are administered to stimulate fetal lung maturity in situations where there is a risk of preterm birth. The best choice for this purpose is usually betamethasone or dexamethasone. These medications are typically given to pregnant individuals between 24 and 34 weeks of gestation when preterm birth is imminent. The correct answer to when are glucocorticoids used and which one is the best choice is b) After 34 weeks; betamethasone, as it has been shown to be effective and has fewer side effects on both the mother and the fetus than other glucocorticoids. It is important to note that after 34 weeks, the added benefit of glucocorticoids decreases because the fetal lungs are more likely to be sufficiently matured.