Relationship between dating age and pregnancy
If this happens, your doctor will not be alarmed but she'll keep an eye on how your baby is developing in subsequent scans just to be sure that the difference in age doesn't increase.
You may also find that your scan report indicates different ages for different body parts of your baby.
This is completely normal as each baby has different proportions and grows slightly differently.The size of the baby correlates less and less with its age as time goes on.Ultrasound examinations from 12 to 22 weeks are regarded as being within 10 days of accuracy (or up to 10 days earlier or 10 days later than the woman's calculated due date).She will ask you when the first day of your last period was and from there, count how many weeks pregnant you are.
This is also how your doctor will estimate your due date by counting 40 weeks from the first day of your last period.
An ultrasound scan estimates your baby's age by measuring different parts of your baby's body such as her head, abdomen, and legs.