Is having a baby 100% safe?
Is lying down to go to sleep safe while pregnant 100% safe?
Pregnancy massage is as safe as those two activities, which are not 100% safe.
As Masthera said, if there are no complications, pregnancy massage is safe - I'll add when performed by a qualified therapist after the first trimester - after the first trimester because there is generally a much higher risk of miscarriage in the first trimester, not that there is a higher risk of miscarriage due to a massage. It is actually not that much of an issue since most people don't start looking for pregnancy massage until after the 3rd trimester anyway, or at only about 10wks, easy to wait a couple more weeks.
There are points to avoid during a pregnancy massage as they supposedly can stimulated uterine contractions which is where the "qualified therapist" comes into it. I always wondered exactly how much stimulation was required and of all the "I'm fed up, do something!" at about 37-38wks I've had recently, I've worked on some of those points and all 5 have gone into labour within 24hrs (with no issues, all babies fine) after carefully avoiding those points for months, so I think the points do do something.