Early ultrasound for pregnancy dating
Charts have been developed for this purpose, but some simple rules of thumb can also be effectively used.
From 6 to 11 weeks gestational age, the fetal CRL grows at a rate of about 1 mm per day.
Occasionally the nasal bone cannot be seen at 11 weeks as it is too early in the pregnancy.
Occasionally the view is not clear and it may be necessary to perform a vaginal scan.
Accuracy of CRL after 12 weeks in predicting gestational age diminishes and is replaced by measurement of the width of the fetal head (biparietal diameter or BPD).
The nuchal translucency (also spelled nucal translucency) is a collection of fluid beneath the fetal skin in the region of the fetal neck and this is present and seen in all fetuses in early pregnancy.
You do not need to have a full bladder, a moderately filled bladder is needed for a proper examination.
Most parents look forward to their scan because it gives them the first glimpse of their baby.