Possible, but apparently more a theoretical risk. Certainly small compared to other birth risks.

Until a few years ago, C-section was recommended, but the current wisdom is that vaginal birth poses no greater risk for the baby.

Same with breastfeeding. Until a few years doctors would call CPS if a HIV+ woman admitted to breastfeeding her child. Now, our doctors encouraged my HIV+ wife to breastfeed.

OTOH she was the second (or third?) HIV+ woman in our city who dared to.

Worked out for us. Both kids are HIV-, as am I.