My first ultrasound said i was 14 weeks one day pregnant but my lmp put me at 16 weeks 4 days pregnant. could the ultra sound be off by 16 days. How many days off could a 14 weeks ultrasound be.?

Yes it can be off, they usually are within about 2 weeks of the due date, it is just a round about date that they give, but usually they just tell you when they think the baby is processing too. So maybe when they do the one at 20 weeks, they will let ya know if it has changed....Good Luck Darlin!! :)

To elaborate on the previous response a little more...when the doctor or technician tells you that you are 14 weeks, the fetus is actually around 12, if they tell you that you are 12 weeks, 3 days pregnant, then the fetus is 10 weeks, 3 days. It is too difficult to determine the actual date of conception based on the first day of your last period so they typically round up 2 weeks to make it even...it's sort of goofy but based on your question I'd say your second U/S was showing you only 4 days different from your first...I imagine your U/S was giving a fetal age of 14 weeks and the LMP was more of the 2 weeks different date around 16 weeks...only it was 4 days different...make sense? :) Best of luck!