How i can know about the gender of my baby i m pragnant and 12 weeks pass my fetal heart beat is 170?

No correlation : Unfortunately there is not a correlation between fetal heart rate and gender. You can find out at your 20 week ultrasound. We can now detect fetal sex by a blood test called non invasive perinatal testing but unfortunately that is only available to women over the age of 34 (>35 when they deliver) or those that are high risk for having a fetus with a chromosomal abnormality.

Ultrasound: Try an ultrasound examination for definitive answer. The heart rate is not specific enough.