No. Given an extremely good side image that capture both the spine and nub, a skilled sonographer can sway their guess one way or the other, but there is no real way to say with any certainty at 13 weeks involving an u/s.
The materniT21 blood test can screen for the presence or absence of the Y-chromosome in free-floating DNA fragments from the baby in the mom's blood stream. And, PGD testing during IVF can make the determination, again genetics. But, those are the only two non-invasive ways to tell before the sex organs undergo transformation in the 15th week.