Multiple pregnancies

Okay I know this is kind of a dumb question. Well not really because I obviously don’t know and no question is ever really dumb. Anyways I went for a prenatal screening today and they had me urinate in a cup to confirm my pregnancy there and I am which i already knew but on the paper work she gave me she circled yes on the multiple pregnancies part. On my sonogram from another doctor it was only one baby so I’m confused? Can that be detected through urine ?