I take 4000 to 5000 IU of D3 a day. I'd easily feel fine with taking up to 8000.
Doctors are great resources, & I'm thankful for mine, but they are only human. Many simply don't have the time or inclination to look into newer research (particularly in areas such as vitamins). As a patient, you have a right and a responsibility to think, research, and advocate for yourself (& your baby).
Either way, I agree that it's up to you.