If your obstetrician is on vacation, I suggest that you ask for a referral to a perinatologist (an obstetrician with specialized training in high risk pregnancies). They can review your history and ultrasound and give you an informed opinion about the significance of the placental calcifications.
The good news is that your baby is likely to do well since you're at 34 weeks and the baby is growing normally. Even if your doctors decide on an earlier delivery than your due date, babys that are past 34 weeks of gestational age generally do extremely well.