Leaning boy, they no longer have a 'nub' at 16 weeks as their bits are fully formed by 16 weeks.
I'm going to say boy if you're at 16 weeks. Guessing nub shots are usually done from about week 11-14. It was very clear my son was a boy at 16 weeks. I would say you're looking at his pee pee
At 16 weeks I'd guess a boy as they cautiously do gender scans from 16 weeks as the genitals are formed enough to make a guess. If you see something between the legs I'd say boy. Not sure on this pic if that between the legs or the umbilical cord!?! X