Help me solve this if possible?

Sara • FTM • DD Nov. 24 but born Nov.19 • Happily Taken❤️
Okay so I've been hearing a lot about if the heartbeat is higher then it's a girl or boy and so on if it's low it's a boy or girl.. etc. This isn't true right? My babies heartbeat was at 185.. and my sister predicted lmao and insisted it's a girl. 😂😂😂😂