If a pt requests an prescription for a +ve group b strep infection prior to delivery, can this prevent ascending infection resulting in chorioamnionitis in l&d?

Not reliably: This was tried in controlled studies in the past and found ineffective in reliably eliminating group b carriage.One likely problem is gbs is a common inhabitant of the intestinal tract & oral medications likely can't reach all the germ traveling within the stool. Standard rx is to give IV meds in labor to surpress/kill any residual germs. Such protocols have dropped infection rates substanti.