Almost all women have ultrasounds during pregnancy. This test allows your health-care provider to see an image of the baby using sound waves. Ultrasounds are recommended for all women over age 35.

Ultrasounds are used to determine or confirm due dates, look for multiple babies, check the baby's development, record heartbeats, measure the amount of amniotic fluid, and screen for abnormalities. Finding out the baby's sex can be one of the perks of this test, if you want the information. An ultrasound is performed by a health-care provider who moves a handheld probe over the mother's uterus. Ultrasounds have no impact on the baby and are usually not uncomfortable, although you may need to have a full bladder for the test. If you have an ultrasound early in pregnancy or if you need one later in pregnancy to assess your cervix or to exclude a placenta previa or low-lying placenta, you will have a vaginal ultrasound. In this type of ultrasound, a probe is inserted into your vagina and gently moved, and an ultrasound image is generated that way. This is not painful, and you do not need to have a full bladder. It is also important to realize that this will not cause a miscarriage or any harm to your baby or the placenta.

A genetic ultrasound is a method of assessing for chromosome problems in women 35 and over. This is usually performed at sixteen to eighteen weeks. The ultrasound looks for markers and features of chromosome problems. If none is found, then the risk of trisomy 13, 18, or 21 is reduced by a certain percentage. The test cannot completely rule them out, but it can indicate the degree by which your risk is reduced. Some women use the genetic ultrasound to decide whether or not to have an amniocentesis. This method significantly reduces the need for amniocentesis. It is, however, very dependent on the skill and experience of the obstetrical sonographer.

The first ultrasound is usually done around sixteen to twenty weeks (although some are done earlier to date a pregnancy, check for twins, or rule out an ectopic pregnancy). Later ultrasounds may be done during amniocentesis, to check positioning of the placenta, or to estimate birth weight. High-risk pregnancy may require more sophisticated ultrasound assessment using high-resolution ultrasound equipment and specialized testing such as fetal echocardiography (for a detailed evaluation of the baby's heart), or Doppler ultrasound (to measure velocity and flow of blood in fetal and uterine blood vessels). Generally a maternal-fetal medicine specialist performs such specialized surveillance.

Routine ultrasounds are usually performed by ultrasound technicians, and the results are then read and interpreted by a physician. This physician may be an obstetrician, radiologist, or maternal-fetal medicine specialist. Some obstetricians may hire an ultrasound technician to work full-time or part-time in their office so that the ultrasound may be done onsite. Generally, ultrasound results performed under the supervision of an obstetrician or maternal-fetal medicine specialist will be made available at the time of the scan. Results performed under the supervision of a radiologist generally are not shared with the mother at the time of the scan but are later reported to your obstetrical care provider, who then discusses the results with you.

It is important to remember that both the quality of the ultrasound imaging equipment and the skill and experience of the ultrasound technician and reading physician are extremely important. You will get the best results from a facility or practice with a lot of experience in obstetrical sonography. Sometimes, there may be a question of an ultrasound finding and a referral to a maternal-fetal medicine specialist or ultrasound unit will be recommended. If this happens, you should not panic, since most of these findings turn out to be nothing.