I've been a SAHM since my dd was born (she's now 10). She didn't go to preschool until the year before kindergarten. She hadn't spent much time in a structured setting and I wanted her to have that experience. Also to have the experience of being away from me for an entire morning.
Well, I did teach preschool part-time when she was not quite 2. During that time, she went to a Moms' Day Out program (I used the time for planning) one full day per week. She absolutely loved it and had so much fun there! She was a very social little thing and loved be around lots of people.
We also belonged to a moms' group since she was a few months old. We met weekly as a group with the kids and also had frequent playdates. Dd went to preschool 3 mornings a week just for the year before kindergarten. It's our community preschool and I mainly sent her to support our preschool and get to know some neighborhood kids and moms.
Pros? She learned a lot of things and had fun. It gave me some "me time" and time to run errands and do housework so I could spend more time playing with and doing things with her when she was home. Cons? I honestly don't think there were any except perhaps we could have saved some money by not sending her.
Be honest with yourself. How much are you playing with her? How often are you getting out and doing activities with her? How often are you having playdates with one or more children? Are you involved in mom and child activities outside the home as well? If you're doing all these things, they're just as beneficial as preschool, imo, but going to preschool can only serve to broaden her world. (and yours!)
Your comment about the study is what I have read also. I think it really depends on how rich the home environment is.
