today i had my US and the heart rate was 140 , i know above 140 a girl and below 140 a boy but what about 140 ...

well, its all hogwash. my boys were always high 150s and low 160s.  so is my girl.  i think it has more to do with activity level.  i have active babies.  and active children!!  lol 

Read what Maureen posted about it.   

 http://www.in-gender.com/cs/forums/t/26887.aspx

My boys were over 150 and this time it's a girl and I've had 150, 146, and the last one was 140. I think it's activity level as well.

my last one was always 120-125 and she is all girl..even my Dr.said she thinks its a boy before US..

 I have actually been told by several midwives that it isn't the heartrate during the pregnancy that matters but the heartrate during actual labour....they can usually tell if it is a boy or girl by the heartrate of the baby during labour so if your babies heartrate is below the 155's its usually a boy and above is usually a girl....that actually worked for me both times as during labour their heartrates were around the 140 mark - however their heartrates during my pregnancy were both higher than 150+ which would mean that they should have been girls.

hope it's not true all pg's were above 150, first 2 were girls I don't know the sex of me 3rd

KatesDreamGirl:

well, its all hogwash. my boys were always high 150s and low 160s.  so is my girl.  i think it has more to do with activity level.  i have active babies.  and active children!!  lol 

Oh dear then I'm in for another active bubby!!!! DD doesn't sleep - plays until she falls asleep usually in the place she's playing Her heart beat was 167 this one is 165.....great............

My girl was always over 160, and my boy was always right around 140 (usually just a hair over). Granted, she is HIGH energy (always has been) and he is calm as can be. I think it is more a personality thing than an accurate predication.

I'm prego now, and this one's always in the 160's, so we will see what it turns out to be!

Good luck!

I heard that it is accurate if during labor, like someone else said.  I don't know what my son's heart rate was during labor, but all my girls were in the 160s.  So maybe it is true.