Thank you for your consult at DoctorSpring.com.
Yes, Adderall is a pregnancy category C drug. Its risks in humans have not been studied adequately.
However, all major organ systems develop in the second trimester, when you were drug free. After 33 weeks drug intake is relatively safe.
Still, an ultrasound is a must. Please insist on a detailed ultrasound scan.
There is no much extra scrutiny that can be done in the third trimester, however, an ultrasound scan in expert hands is required.
All the best.
Please feel free to discuss further.