You started your period December 1 and ended December 6 your ultrasound says you are 9 weeks pregnant when did you conceive?

If your period started on December 1 and lasted until December 6, you likely ovulated around December 15, assuming a typical 28-day cycle. If your ultrasound indicates you are 9 weeks pregnant, that would place your conception around December 15, making your estimated due date around September 24. The 9 weeks of pregnancy typically counts from the first day of your last menstrual period (December 1), not the conception date.