On some occasions it is still difficult to see and so we may ask if a more detailed internal ultrasound scan can be done trans-vaginally.
This is a simple procedure and does not cause any pain or harm to the pregnancy.
Your midwife or doctor will book you a dating scan appointment.
It will usually take place at your local hospital ultrasound department.
The person performing the scan is called a sonographer.
Ultrasound scans use sound waves to build a picture of the baby in the womb.
The scans are completely painless, have no known side effects on mothers or babies, and can be carried out at any stage of pregnancy.