Expert: Catherine Beier MS CBE - 5/19/2009

Question
My calculated dates says that I'm seven weeks pregnant but the ultrasound measures five weeks. Is this cause for concern or is it normal?

Answer
Kellie,

The answer depends upon how the dates were calculated.  If they said the fetal age is 5 weeks, then yes, this is normal.  The baby is always 2 weeks younger than you are pregnancy because pregnancy duration is typically calculated from the first day of your last period, meaning that for the first two weeks, you're not pregnant yet (I know it's confusing).


If you are supposed to be 7 weeks based on the date of your last period but the measurements are showing 2 weeks behind, then this could mean a couple of things.


First, it could simply mean that you ovulated late in your cycle and/or have long/irregular cycles which makes the first date of your last period an unreliable way to date the pregnancy and can account for the discrepancy in measurements.



It could also mean that there's a problem with the pregnancy and that the baby isn't developing as it should.  



So, at this point, it's impossible for me to say what is hapening in your case.  The best course of action is to ask your care provider since they have access to your records and ultrasound results.  Any time you have questions, don't hesitate to ask them.  If you don't understand the explanation, then keep asking until you do.  That's what they're there to do, to help you make informed decisions for your care and they are responsible for making sure you understand what is going on and what your options are.


So, at this point, it's too soon to worry until you have all the facts and know exactly how the measurements were taken and what they suspect is going on.



Best,
Catherine