yes twigglet, I have heard this as well.
But its usually lower for a boy higher for a girl,
Being really sad, whenever I watch a birthing programme, I try to get a quick look at the monitor to try this theory out.(Yes I do need to get a life)
And I have to say, I usually predict correctly :0
But 142 seems to be middle ground, I wouldn't be sure about that.
If it was 120 or 130 I would say defo a boy. Above 150 defo a girl.
Having said that I was hospitalised at 35 weeks cause babe had a fast heatbeat and he turned out to be a boy:0