Would you talk to the principal?

I have a nine year old son starting fourth grade. For the last two years he has had teachers who were pregnant and left half way through the school year (one came back after eight weeks, the other was gone the rest of the year). Tonight we found out that his fourth grade teacher is pregnant and will be taking a leave in the middle of the year. I am very tempted to talk to the principal and ask to have him moved to a class where for the first time since first grade, he’ll have the same teacher for the entire school year. Any thoughts?