Start First trimester dating ultrasound accuracy

First trimester dating ultrasound accuracy

In early pregnancy, the measurement from the top of the fetal head to the bottom of the pelvis is called the “Crown-Rump” length.

If you do know the conception date, this is classed as day 14 and not day one.

If you have an irregular cycle, or if you've recently been taking the contraceptive pill, working out the date from your LMP isn't a very accurate method.

So in this arithmetic test, the baby sets the curve.

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.

Ultrasounds are more accurate than using the LMP and, if the ultrasound date differs from your period dates, the ultrasound date will be used.

The ultrasound date is usually later than the period date, so accurate dating has been found to reduce the number of women having labour induced because their babies are overdue The ultrasound can check that your baby has a heartbeat and is developing normally.

Your baby's head, limbs, hands and feet, and some organs can be seen, and - though looking for abnormalities isn't the purpose of the ultrasound - some major problems can be seen at this early stage.