Slide show: Fetal ultrasound

A fetal ultrasound can give you an early glimpse of your baby, but it isn't done primarily for parental thrills. A fetal ultrasound allows your health care provider to evaluate your baby's growth and development and determine how your pregnancy is progressing.

Wonder what to expect? Here's a look at real fetal ultrasound images, as well as tips for understanding the images.

During a fetal ultrasound, your health care provider rubs a small device called a transducer across your belly or inserts a probe into your vagina. High-frequency sound waves are translated into a pattern of light and dark areas — creating an image of your baby on a monitor.

In this slide, you see a baby's profile at 11 weeks of pregnancy, or nine weeks after conception. A baby's head makes up about half of his or her length at this stage.

This slide offers a four-chamber view of a baby's heart — a reassuring sign of normal heart development.

A baby's cardiovascular system begins developing five weeks into pregnancy (three weeks after conception). The heart starts to beat shortly afterward.

Here you see the base of a baby's brain. The shape of the cerebellum — the part of the brain that controls muscle coordination and balance — is important in the detection of neural tube defects.

The neural tube forms in the first few weeks of pregnancy. The top of this tube becomes the baby's brain, and the rest becomes the spinal cord. Problems in neural tube development may lead to conditions such as spina bifida, in which the spinal cord may bulge out through an opening in the spine.

This is a view of a baby's head. The thick white lines that form a circle near the top of the image indicate the baby's skull. The white line in the middle of the circle is the midline structure that separates the baby's brain into symmetrical halves.

Measurements of your baby's head can help your health care provider determine your baby's age.

Here you see a baby's open hand and fingers — another reassuring sign of normal growth and development. Images of an open hand can help the health care provider rule out certain chromosomal abnormalities.

Any guesses about this image? It's the lens of a baby's eye.

Twenty-three weeks into pregnancy, or 21 weeks after conception, a baby begins to have rapid eye movements. A baby's eyelids begin to open 28 weeks into pregnancy, or 26 weeks after conception.

This slide is a cross section of a baby's cervical spine. The cervical spine — which begins at the base of the skull — protects the spinal cord and supports the skull.

This image may be easier to decipher than the others. Look carefully, and you can see the curve of a baby's spine.

Now you're looking at a baby's femur. This leg bone is the largest and strongest bone in the body, extending from the hip to the knee. Along with various other measurements, femur length provides important information about your baby's age.

On this split screen, check out the lower legs. The baby's knee is on the right side of each image, and the ankle is on the left. You can also see the shinbone (tibia) and the small bone on the outside of the ankle (fibula).

Do you know what you're seeing here? The arrow points to the site where the umbilical cord is attached to the baby's belly.

By examining this area, your health care provider can identify or rule out conditions such as the protrusion of abdominal contents through an opening at the navel (omphalocele) and a break or split in the tissue that forms the abdominal wall (gastroschisis).

For parents, this may be the most touching of all ultrasound images — baby's profile. Did you notice the baby's hand resting on his or her knee?

A 3-D fetal ultrasound can provide images of a baby with photo-quality details. This type of ultrasound is used in select medical centers to help health care providers evaluate a baby's growth and development. 3-D ultrasounds are also available commercially — but the use of fetal ultrasound solely to create keepsakes isn't recommended.