I am not sure if they have increased the iron Willow - I've not heard they have...
No with that high progesterone Willow it will stay that way and that as you say increases the old constipation! So, perhaps that is why you are more constipated this time around. As I said above if it's a real issue I would change to another prenatal vitamin and take a natural iron supplemnet like Floradix etc...

Like you I had off the chart progesterone (320) at 15dpo and I know what it can do to the bowels!!!! If I went near iron at the moment I would be in trouble I think!