Accuracy of dating pregnancy with ultrasound
The software has certain measurement scales based on data from large populations, and your baby’s measurements are put into this scale.
In other words, by comparing your baby’s measurements to the data from this large collection of measurements, the ultrasound can then tell how far along your baby is.
The computer in the ultrasound (ignorantly) lumps your bigger baby into the dates of babies that big in the “normal” population.
This may then indicate that your 37-week baby is two weeks overdue!
A small amount of ultrasound gel is placed on the end of this probe.
The probe is then gently inserted a short distance into the vagina.
For instance, say you normally have eight and nine pound babies.
A small amount of ultrasound gel is put on the skin of the lower abdomen, with the ultrasound probe then scanning through this gel.
The gel helps improve contact between the probe and your skin. It involves scanning with the ultrasound probe lying in the vagina.
Transvaginal ultrasound usually produces better and clearer images of the female pelvic organs including the developing pregnancy, because the ultrasound probe lies closer to these structures.
The transvaginal ultrasound probe is thin, about 2cm diameter.
The probe is covered with a disposable protective sheath.