An ultrasound, or sonogram as it is sometimes called, is a noninvasive diagnostic test that uses sound waves to create a visual image of your baby, placenta, and uterus prior to birth. It allows your doctor to collect important information about the progress of your pregnancy and your baby’s health.

During the test, an ultrasound technologist, also called a sonographer, transmits high-frequency sound waves through your uterus that bounce off your baby. A computer then translates the echoing sounds into video images that reveal your baby’s shape, position, and movements.

Early on, an ultrasound may be used to estimate the age of your pregnancy, especially if your menstrual cycle is abnormal or much grater than 28 days. You may have an appointment for Nuchal Translucency, which is also done by ultrasound, checking your baby’s risk for Down Syndrome and other chromosomal abnormalities.

Between 18 and 20 weeks of pregnancy, you will be scheduled for a level 2 ultrasound exam. During this hour long ultrasound exam, the baby is measured from head to toe, to check if the gestation age of the baby is within a normal range. The functioning and development of the vital organs is also monitored during this ultrasound. The sex of the baby can be determined during level 2 ultrasound, so if you wish NOT to know the sex of your baby pre-delivery, tell the technician right from the start.

Depending on the development of your pregnancy, your doctor may decide whether or not you need more ultrasounds. You may have one towards the end of your pregnancy to determine if there is a need to induce labor.