Hi. I'm Mary.. What is the best time for me to have my ultrasound to know our baby's gender. Now, im confuse because my first doc.said my baby is already 18 weeks and when I went to a different OB (I changed doctor since my last doctor is always on vacation) and she said my baby is 15 weeks.My last menstruation was Feb. 24 or 28 wasn't that sure but I know it's last week of Feb. Any advice or comment about how many weeks is baby now.Thanks a lot.