At the end of pregnancy, maternal blood concentrations of E2 are almost 100-fold higher than those of nonpregnant women, reaching 30 nmol/L49,50, whereas placental aromatase deficiency can be detected in women with PE at delivery, and decreased levels of E2 are considered to be closely associated with PE51,52, suggesting the essential role of aromatase in pregnancy. Here, CYP19A1 is linked to hyperinsulinemic hypoglycemia, familial, 4.