I just had a massage! I'm 15 weeks pregnant. It was sooooo wonderful! But I did ask my midwife. And here is what she said. Ideally you want someone who is certificed to give prenatal massages. But if not, then that is ok as long as they take certain precautions. Only lay on your side, not on your stomach or back. Don't let them massage your inner calf (it could induce labor). Don't let them massage your wrists. Also, don't do a deep tissue massage (you don't want all those toxins in your blood when you're pregnant) and don't let them massage your lymph nodes either. My massage therapist wasn't certified in prenatal, but she did a great job anyways.
Have fun!