Women's Health: Postpartum Community
26.1k Members
Avatar universal

20 week ultrasound question

How accurate are ultrasounds at gauging the age of the baby?  At my 20 week ultrasound, my baby was estimated to be a couple days younger than previously calculated in a different ultrasound.  Just curious how normal this is and want to know about others experiences.
7 Responses
164559 tn?1233711618
They are really a guesstimate.....babies come only when they are fully cooked,  due dates are misleading.
Avatar universal
Also I think they say the earlier ultrasounds are more accurate.
Avatar universal
First of all, why worry about just a couple days younger??  If they were off by weeks, I'd be worried. Second, I think they are accurate b/c they look at very specific structure growth that can be timelined (ex. major organs appear certain ways and function or not only past certain time frames) at 20 weeks. Be happy all the structures apparently looked good along w/ amniotic fluid, positioning , etc.  And remember, your general due date probably hasn't changed...
174515 tn?1191710869
it can vary by a week or more. the earlier ones are more accurate, but keep in mind every baby grows at its own rate. an ultrasound guesses age based on a generalized scale of what the baby "should" be at a certain age. not taking into account that babies vary in growth. i think it's fine. my twins have been anywhere from 5 days apart in size to the same day in size , back and forth.
Avatar universal
The Earlier Ultrasounds are more accurate.  I dont think you have a thing to worry about!  be happy!  You have a beautiful baby growing inside you! YAY!
161427 tn?1229914882
During my 20 wks u/s with my first pregnancy, they told me he is gonna be a big boy, at least 91/2lb, He was just 6lb 15oz!!! So, you never know, when the fetus is ready , he will come out to meet us.
Popular Resources
From skin changes to weight loss to unusual bleeding, here are 15 cancer warning signs that women tend to ignore.
Here’s what you need to know about the transition into menopause – and life after the change takes place.
It’s more than just the “baby blues.“ Learn to recognize the signs of postpartum depression – and how to treat it.
Forget the fountain of youth – try flossing instead! Here are 11 surprising ways to live longer.
From STD tests to mammograms, find out which screening tests you need - and when to get them.
Find out if PRP therapy right for you.