It will tell you exactly how many weeks pregnant you are. This measurement, known as the crown rump length, is very accurate in the first trimester. National Institute for Health and Clinical Excellence, clinical guideline 62.
After 13 weeks your baby can curl up and stretch out, so measuring the length becomes less accurate. A randomized trial of prenatal ultrasonographic screening: impact on maternal management and outcome. Antenatal care: Routine care for the healthy pregnant woman.
The sonographer will put some gel on your tummy and will move a small hand-held device, called a transducer, over your skin to get views of your baby. National Down's Syndrome Screening Programme for England.
The dating ultrasound will also show if you're expecting twins, triplets or more.The day of conception depends on: An obvious fact is you cannot conceive until you ovulate; therefore, the most likely date of conception is on the day of ovulation, if there is sperm around.If you can determine that day, you will come close to identifying your date conception.It may show a very minor problem, or something which may get better on its own. As with all screening tests, there can be false positive and false negative results.