Medical OB ultrasound

What is ultrasound?

Ultrasound uses sound waves at a frequency too high for the human ear. As they reflect off internal organs and, during pregnancy, the baby, a scanner reads the echoes and turns them into pictures.

Real-time ultrasound shows those pictures in rapid succession, like the frames of a film. That’s how you can see your baby’s heartbeat, arm and leg movements, growth and the placenta.

What a standard exam can determine

Your provider will decide whether you need an ultrasound and how often. A routine exam can show:

• Whether it’s a single or twin pregnancy
• Fetal heartbeat and viability
• The baby’s position
• Gestational age and estimated weight
• Amniotic fluid volume
• The placenta
• Major fetal malformations
• The uterus and ovaries in early pregnancy

Reading your ultrasound

On the screen, black is fluid and white is bone. Your exam will look at:

Fetal position

Breech (bottom down) or cephalic (head down).

Placenta position and cervical length

To rule out placenta previa, where the placenta covers the cervix.

The brain

Including hydrocephalus (fluid on the brain).

Findings sometimes associated with Down syndrome

Diaphragmatic hernia (an opening in the diaphragm), VSD (an opening in the heart wall), cleft lip, hydronephrosis (fluid backing up in the kidneys), a two-vessel umbilical cord (there should be three) and cord insertion abnormalities.

The spine

To check for spina bifida, where the spinal column doesn’t close completely.

Fetal measurements

Head, abdomen and femur (thigh bone). Your physician usually changes your due date only if the measurements differ from it by two weeks or more.

Arms and legs

Confirming two arms and two legs are present.

Limitations

This exam is designed to detect major defects. It can’t guarantee that every defect will be found: some develop later in pregnancy, and some found at birth couldn’t have been seen earlier. Examining for every possible birth defect requires a targeted study beyond a standard exam. If a serious problem is suspected, you’ll be referred to a perinatologist.

Safety

Ultrasound has been used in pregnancy for decades and has an excellent safety record. Professional guidelines recommend it be performed when medically indicated, by trained professionals, using the lowest exposure needed to get the information. That’s the standard we follow.