Pregnancy confusion

Patient: I have tested on 4 pregnancy tests. 3 being home and 1 being at my doctor’s office. They all came out positive. My last period was Feb 18th so that would put me around 8 weeks? I went into the Doctor’s office and got an ultrasound done last week due to having some pain but when they did the ultrasound they couldn’t see anything so they sent me to a high tech ultrasound where they said they see an early pregnancy possibly around 2 1/2 weeks. How am I testing positive now being possible 3 1/2 weeks? I thought at two I’m still not pregnant and you can’t test positive till 5 weeks? I feel like I should be farther along then they say I am.

Doctor: I understand your concern about discrepancy between Last Menstrual Period vs. Ultrasound Gestational Age. Usually there is some difference between the gestational ages obtained with ultrasound and using the last menstrual period date.It all depends on when you ovulate; conception typically occurs about 11-21 days after the first day of the last period. Most women do not know the exact date of conception, and their conception date is merely an estimate based on the first day of their last period. So if your last menstrual period was on Feb, 18th you could have conceived up to 3 weeks after. So based on your Last Menstrual period you should be around 5 to 6 weeks. Now Ultrasounds usually dont pick up images until 5 weeks. In cases like this, a careful follow up with ultrasounds and blood work looking for the HCG values or Pregnancy Hormone to estimate the Gestational age would be needed. Additionally there is a difference of – 1 week between LMP and Ultrasound that need to be considered too. I suggest you to comply with your pre natal controls to rule out the Exact Gestational age.