The old school of thought was to capture your baby every month, or at least every 3 months (3, 6, 9 months) in their portraits. Now, many folks are moving to an extended timeline to allow for capturing changes all the way through 18 months to the 2 year milestones. The in between stage (from newborn to one year) has a couple different options that we recommend.
If you like the idea of more transitions being captured, then a 4 month and an 8 month portrait would be a good fit for you. At 4 months, we get to see amazing belly poses, naked butts, and some adorable smiles. At 8 months we may get crawling, tripod sitting, and even some laughter.
The second option if you prefer the idea of extending your portraits to 2 years old, is to go with just a 6 month session during the in between stage. You will get great smiles, belly poses, sitting poses, and lots of interaction from your baby. Both options will give you incredible portraits!