The brain

Below is an image of the base of the brain, called the cerebellum. This type of image usually is taken during an ultrasound done between 18 and 22 weeks of pregnancy.

The cerebellum is the part of the brain that controls muscle coordination and balance. Checking its shape on an ultrasound can help the health care team find neural tube defects. The neural tube forms in the first few weeks of pregnancy. The top of the tube becomes the brain. The rest of it becomes the spinal cord. Problems in neural tube development may lead to conditions such as spina bifida, in which part of the neural tube doesn't develop or close correctly. This can lead to problems in the spinal cord and in the bones of the spine.