Chicken pox vaccination

I talk to my gynecologist about starting to conceive. She wanted to get my body ready to conceive. She asked a lot of question and one specific question she ask was have I had chicken pox? I said no. She ask have I been vaccinated and I told her I don't know. She had me do a lot of blood work to check for different vaccination. All was clear but she told me that I was not vaccinated for chicken pox and I should be vaccinated for it. My question is what is the purpose of me being vaccinated for chicken pox while ttc? I never got a chance to ask her this question because the bloodwork results are posted online along with her notes.