Firstly dont panic. Women with hht have been having children for very long time. If you can before you plan to get pregnant would be a very good time to talk to your doctors. Your doctors can look at all your medical information and advise what is best for you. The care you may need during a pregnancy really does depend on how you are affected by hht. 1 out off 100 HHT pregnancies will not end well which is why normally a HHT pregancy be seen as high risk.
If you have not all ready been screened for pulmornary avm's will need to be, they may also wish to check again and may also wish to do MRI scan to check for any spinal avm's if you plan on having an epidural.
Whenever doctors choose to do tests or procedures duing pregnancy the health of you and your baby is their main concern.