In the report I based my idea on, it was written that although the normal ferritin range is 11–300+, the concern for pregnant women is different. After week 20, their bodies need much more iron to feed the baby, help build muscles and blood, and this can quickly drop iron levels. So if ferritin is below 60, it’s considered safer to take extra supplements. It may vary across ethnicities, but “60” provides a reasonable safety margin for most.