bbhp,
dr loh determines gal if he see "3 lines" underneath. dat's hw he explained for mine la.
prob he saw something sticking out for ur 2nd bb, so tell u may be a boy lor.
anyway, healthy bbs more impt than wat genders mah.
even 20wk scan @ ADC may not see gender if bbs dun wan u to see, e.g. hand cover pte part, body keep facing down, etc