Obstetric Ultrasound

Introduction to pregnancy ultrasound

An obstetric ultrasound, also known as a prenatal ultrasound scan, can screen for and diagnose birth defects and / or hereditary conditions. An obstetric ultrasound is an ultrasound of your pelvis which produces an image of the foetus in the uterus.

How do pregnancy ultrasounds work?

A probe is used to pass sound waves into the body. An image of the baby is produced by the reflection of those sound waves. The images (sonogram) are displayed on a television screen. The sonographer performing the ultrasound can explain these images to you. Appropriate use of ultrasound poses no physical risk to you or your baby.

Why would you have a prenatal ultrasound?

You may have an ultrasound to check the development of your pregnancy. This includes:

  1. Confirming the stage of the pregnancy;
  2. Checking the continuation of a pregnancy if there has been bleeding;
  3. dentifying a multiple pregnancy
  4. Checking the position of the placenta
  5. Checking the amount of amniotic fluid
  6. Checking the physical development of the foetus
  7. Diagnosing birth defects and/or hereditary conditions

When would you have an ultrasound?

In first trimester it is common for an ultrasound to be performed to confirm the gestation of the pregnancy. An ultrasound can be performed as part of a screening test at 11-14 weeks to screen for Down's Syndrome. This screening test involves a blood test to measure two hormones, free B-HCG and PAPP-A, as well as an ultrasound scan. The ultrasound measures the nuchal translucency of the baby. It is common medical practice to also offer an ultrasound scan, called the 'foetal anatomy' scan, at 18-20 weeks. This scan looks for the presence of physical abnormalities in the baby. The ability to diagnose physical abnormalities depends on the equipment used, the position of the foetus, the stage of the pregnancy and the experience of the person performing the ultrasound.