There is a chance of affecting the foetus.. did the doctor advise any treatment? Please go for all your antenatal scans and tests to make sure baby’s alright. Also, please go for all vaccinations that are required, to protect your baby from the other conditions that can lead to congential problems
Oh dear, you may find this article helpful take care! https://www.mayoclinic.org/healthy-lifestyle/pregnancy-week-by-week/expert-answers/chickenpox-and-pregnancy/faq-20057886