is this really normal ?

Today I went in for a regular check up, my doctor checked twin As heart beat and it was 136 and he said very good then when he went to twin B it was 171 & from my understanding I've read that as babies get closer to their due dates the hearts kind of slow down and aren't as fast as when they were a few weeks. Well when it read 171 I said wow isn't that high and he said "hmm" scanned around more and then said "everything looks normal to me" but was off to me how he hesitated & ive read several times on here how so many other women's doctors tell them nothing is wrong and something is always wrong... has this ever happened to any twin moms and everything turned out to be ok?? Im 32 weeks & 3 days