Iron is a really important nutrient during pregnancy and requirements for pregnancy are 1.5 times higher during pregnancy due to the 50% increase in blood volume that occurs.
You will likely have testing in your first trimester and at 28 weeks to see if you are iron deficient. Here are some good things to know about iron.
Heme iron (animal source - red meat or dark chicken meat) is 2-4 x better absorbed than non-heme (plant based) iron. You can also get heme iron from oysters, clams and sardines.
Plant sources of iron have compounds that inhibit iron absorption, like phytic acid, oxalates, and certain polyphenols. If you consume non-heme sources of iron with citrus fruit and some form of citric acid, you can increase absorption. So if you have a green salad (spinach, kale, or butter lettuce) with a citrus fruit (grapefruit or orange) and a vinaigrette dressing, you will absorb more iron. Iron absorption will also be increased if you don't have dairy (or calcium supplements, like Tums) at the same time you are eating non-heme sources of iron.
Iron supplements may be recommended if you are iron deficient. These are important, to reverse an iron deficiency, but can be hard on your stomach and often contribute to constipation. If you need an iron supplement, taking it with a citrus fruit and avoiding dairy at the time of taking the supplement, can help increase absorption.
Liver is the richest source of iron / heme iron, which is very well absorbed and therefore less likely to cause constipation than other iron sources. Liver is also a great source of Vitamin B12 and folate. Thankfully, liver tends to be relatively inexpensive. However, when buying liver, source matters. Consuming a healthy, organic, pasture-raised liver would be ideal.