When you're pregnant you are always checking on a million different things when it comes to the baby, especially the size! Here's a size by size of your baby by each week!
Week 4: Size of a Poppyseed.
Week 8: Size of a Raspberry.
Week 12: Size of a Plum.
Week 16: The size of an Avocado.
Week 20: Size of a Banana.