Pregnancy test line theory..

soo ... i just heard of this theory..

that if your pregnancy test has a dark second line that means girl , due to more hormones in your system (when testing before your missed period) .. obviously you would get a dark line if you tested after your missed period and a faint test line means a boy..

how true can that be?? ... my line 2 days before my missed period was VVF .. and my sisters was also the same and its confirmed shes having a boy, where as my sisters friend got a dark very noticeable line the day before her missed period and she had a girl..

just a theory ive been thinking about now..