Alphabet blocks are a great tool to have in your prop box. They can be used for just about any age child and to spell just about anything.
With babies I lay the blocks in front of the little one and use them to spell out their name.
With maternity sessions, you can use the blocks to spell out the gender or name of the child.
I have used alphabet blocks to spell out the age of a child, the wedding date of a couple and the word senior for high school seniors. They are fun, colorful and pretty affordable. You can often buy them at craft stores using a 40% off coupon. My particular blocks are Melissa and Doug, I love the vibrant colors and the way they personalize any photo.