Mean Sac Diameter (MSD) Calculator
Health & FitnessCalculate the mean gestational sac diameter from three ultrasound measurements and estimate gestational age.
Estimated Gestational Age
Estimated gestational age in days, calculated as the mean sac diameter plus 30.
Mean Sac Diameter
20.0
The average of your three gestational sac measurements.
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Odeh Ahwal0people find this calculator helpful
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Calculator Stats
Creators
Odeh Ahwal0people find this calculator helpful
Views
Helpful
Saved
Embeds
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Frequently Asked Questions
What is mean sac diameter?
Mean sac diameter is the average of three perpendicular measurements (length, width, and height) of the gestational sac seen on an early ultrasound, before the embryo itself is visible.
How accurate is gestational age from mean sac diameter?
This method has an accuracy of roughly plus or minus 5 days, making it useful for dating very early pregnancies before crown-rump length measurement becomes possible.
When is mean sac diameter used instead of crown-rump length?
Mean sac diameter is used earliest in pregnancy, before an embryo is visible on ultrasound. Once an embryo can be measured, crown-rump length becomes the more accurate dating method.
What if I only have one measurement of the sac?
For the most accurate result, use all three perpendicular measurements. A single measurement alone is less representative of the true average size of the sac.
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