PI value is above the 95th percentile

Does anyone know anything on this. I'm currently 26 weeks and my reading for umbilical artery (PI) last week was 1.58, where as the one I got on Tuesday was 2.04. My doctor seemed worried so she sent me to a specialist and the specialist just checked the results and said it was fine, but didn't check with the Doppler device. So I'm a bit confused. What did yours read around this time and was it considered normal?