If you are pregnant and interested in starting orthodontic treatment, I will generally advise one of two things:
1) Seek approval from the OB/GYN to take a Panoramic x-ray, or
2) Wait until after the baby is born to start treatment. The reason is that it is important to ensure good root health and rule out any underlying surprises prior to treatment and this can only be done effectively with an x-ray.
If you are already in the midst of treatment and find out you are pregnant- Congratulations!... and Do not worry! You can continue your orthodontic treatment. I do ask that you please let me know- not just so that I can celebrate with you (because I will!), but also so that I can make sure to take the precaution of holding off on taking any mid-treatment or final x-rays until after the baby is born. Luckily we do not need to take very many x-rays during the course of orthodontic treatment, so often these can be delayed until after the baby’s arrival!