An epidemiologist in Mumbai is studying the relationship between maternal anemia during pregnancy and adverse birth outcomes (low birth weight, preterm delivery). She recruits 2000 pregnant women at their first antenatal visit, measures hemoglobin levels, and then follows them prospectively until delivery, recording outcomes. In contrast, a colleague in Bangalore begins with 800 mothers of low-birth-weight infants and 800 mothers of normal-birth-weight infants, then retrospectively assesses their hemoglobin records from pregnancy. Which statement best compares these two approaches?