One of my favorite things to do while I was pregnant was track the growth of my baby. Every Sunday night my husband and I would sit down and I would read all of the developmental changes that were going to happen for that week.
I also loved watching videos that illustrated what was happening in my belly.
This video shows your baby from conception to birth. It is done via 3D modeling with animation.
It is the most extensive video I have ever seen on fetal development. The students list all changes each week with an approximate weight at each stage. Enjoy!