Obstetric Ultrasound

Ultrasound is safe and painless, and produces pictures of the inside of the body using sound waves. Ultrasound imaging, also called ultrasound scanning or sonography, involves the use of a small transducer (probe) and ultrasound gel placed directly on the skin. High-frequency sound waves are transmitted from the probe through the gel into the body. The transducer collects the sounds that bounce back and a computer then uses those sound waves to create an image. Ultrasound examinations do not use ionizing radiation (as used in x-rays), thus there is no radiation exposure to the patient. Because ultrasound images are captured in real-time, they can show the structure and movement of the body’s internal organs, as well as blood flowing through blood vessels.

Ultrasound imaging is a noninvasive medical test that helps physicians diagnose and treat medical conditions.

Obstetrical ultrasound provides pictures of an embryo or fetus within a woman’s uterus, as well as the mother’s uterus and ovaries.

A Doppler ultrasound study may be part of an obstetrical ultrasound examination.

Doppler ultrasound, also called color Doppler ultrasonography, is a special ultrasound technique that allows the physician to see and evaluate blood flow through arteries and veins in the abdomen, arms, legs, neck and/or brain (in infants and children) or within various body organs such as the liver or kidneys.

During an obstetrical ultrasound the examiner may evaluate blood flow in the umbilical cord or may, in some cases, assess blood flow in the fetus or placenta.

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.

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

A prenatal diagnostic ultrasound can detect physical abnormalities including:

There are two ways in which obstetric ultrasound can be performed.

Vaginal ultrasound is less commonly performed. It is usually restricted to the first trimester (up to 12 weeks) of pregnancy. The bladder needs to be completely emptied in order to perform this method of 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.

For standard diagnostic ultrasound, there are no known harmful effects on humans.