Another way to predict is see who reached orgasm first during intercourse.
If the husband come first, the baby generally will be a girl.
If the wife comes first, most likely it is a boy.
Reason, (scientifically) the eggs produced by the female species contains the chromosome X & Y. The eggs containing the Y chromosomes is found deep in the women uterus. So when the man reached orgasm and ejaculates first the sperms containing X chromosomes (note only X, no Y) meets the eggs nearest to the point of its entry, abundant eggs with X chromosomes can be found and thus a XX baby (a girl) will be formed.
Just my 2 cents worth of opinion.

Cheers.