3 doctors weighed in:

Can a 7-8 week vaginal ultrasound be a month off with dating the gestational age/due date?

3 doctors weighed in
2 doctors agree

In brief: Not likely

A 7-8 week vaginal sono should be within a week of the actual date of conception plus 2 weeks.
The gestational age is expressed as weeks since last menstrual period (lmp) and assumes conception 2 weeks later. If you are 4 weeks less than expected you conceived one cycle later. Due date is an estimate of 40 weeks since the lmp and assumes you will carry full term and not be late or preterm.

In brief: Not likely

A 7-8 week vaginal sono should be within a week of the actual date of conception plus 2 weeks.
The gestational age is expressed as weeks since last menstrual period (lmp) and assumes conception 2 weeks later. If you are 4 weeks less than expected you conceived one cycle later. Due date is an estimate of 40 weeks since the lmp and assumes you will carry full term and not be late or preterm.
Dr. Bruce J. Stringer
Dr. Bruce J. Stringer
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