depends how many weeks you are. My OBGYN told me up to 10 weeks its between 160 and 190 and after that normal is 120 to 170. Hope that helps.
My lil girls heartrate was not far from that at around 9 weeks
164 is good. My second son was usually in the 180s.
the heart rate goes up if they are moving around alot. maybe you just have an active baby,