I thought about this off and on lately just because I have to prepare for when I have my kids. Correct me if I'm wrong, but I imagine it's as simple as just eating a nutrient-dense RPD is what we need. But no skipping out on stuff like organ means, because these would be essential for pregnancy and breast feeding.
I've listened to a lot of stories of women who eat SAD but had major cravings for organ meats while pregnant. Just recently too a women was telling her friend about how she suddenly craved liver like crazy, but she didn't eat it because it's "high in cholesterol and protein." .... I don't even know. But it suggests that we definitely need those nutrient-dense foods like organs while pregnant to supply the baby. I imagine it's similar when breast-feeding, we want the milk to be nutrient-dense too.
