My husband and I have been married 5 years, we just found out that we are pregnant, what concerns are there, his viral load is undectectable.

With unprotected sex, there is always the chance that he could pass the virus to you; with undetectable viral load, the chance is lower but not nil. You discuss this with your obstetrician and should be tested for HIV infection. Women who acquire HIV infection during pregnancy are at higher risk of transmitting the virus to their babies. Going forward, I would recommend that you practice safe sex to minimize the likelihood that you will be infected. There is a lot of good information (and a Forum) on safe sex on this web site. If you are infected, early detection and antiretroviral therapy can markedly reduce the risk of transmitting the virus to your baby. The "Guidelines for the Use of Antiretroviral Agents During Pregnancy" (available on this web site under "Treatment Guidelines" has lots of good information on mother-to-child transmission of HIV (and how to prevent it).