Why nurse called my daughter premature?!

I gave bith to my first child at 37 weeks and 6 days. She was born 5 pounds and 7 ounces she was completley healthy just she had jaundice . Well my monsters in law came after birth and i was asking the nurse why my daughter has jaundce she said because ur daughter PREMATURE. Well at that point i didnt have any info about premature babies and not premature babies so i didnt say anything. My daughter is 4 now and my monsters in law still have problem by telling me ur daughter was born 2 months early and why she born at that tjme why she was small. Omg im so tired with them i dont know how to shut thier mouth. Any advice?