Obstetrical ultrasound is a safe, noninvasive procedure that uses sound waves to create images of the fetus, placenta and amniotic fluid. These images can be viewed in real time on a computer monitor by both patient and doctor. These are the first images parents are able to see of their unborn child.
An obstetrical ultrasound is performed several times throughout pregnancy to monitor the growth and development of the fetus. During the first trimester, an ultrasound can determine the age of the fetus or screen for any potential birth defects, such as Down syndrome. Later in the pregnancy, regular ultrasound exams will measure the size and position of the fetus, placenta and amniotic fluid to ensure that there will not be any major complications during delivery.
Preparing for the Procedure
Patients should drink plenty of water before an obstetrical ultrasound. A full bladder usually provides a clearer image of the fetus. It is best to wear loose-fitting, two-piece clothing that allows the lower abdomen to be easily exposed. A transvaginal ultrasound does not require a full bladder or access to the lower abdomen.
The Ultrasound Procedure
An obstetrical ultrasound is usually performed right in the doctor's office during a regular visit. This procedure can be performed either transabdominally or transvaginally.
A transabdominal ultrasound involves applying a gel to the lower abdomen and moving a handpiece, or transducer, across the skin. This exam requires a full bladder that should not be emptied until after the procedure is over. Transabdominal ultrasounds take 30 to 60 minutes to complete.
A transvaginal ultrasound involves the insertion of a transducer into the vagina and rotating it for a comprehensive view of the fetus and surrounding organs. Patients may experience some mild pressure, similar to that experienced during a regular gynecological exam. There is no special preparation needed for this procedure, and it is usually completed in 15 to 30 minutes. A transvaginal ultrasound provides more detailed images of the uterus and ovaries and is especially useful in the early stages of pregnancy.
Results of an Obstetrical Ultrasound
The results of this procedure are visible immediately for the doctor and patient to view. More detailed results are usually available within one to two days, which the doctor analyzes for any additional information. Normal results indicate a healthy, growing fetus with a normal heart rate and no visible signs of birth defects.
An abnormal ultrasound may indicate a fetus that is too small or underdeveloped for its age, in a breech position or has a birth defect. It can also indicate other problems such as an ectopic pregnancy or a lack of fetal heartbeat. If abnormal results occur, additional testing or a procedure to address the abnormality may be performed.
Risks of an Obstetrical Ultrasound
There are no major risks or complications associated with an obstetrical ultrasound for either the mother or fetus. Ultrasound is one of the most commonly performed diagnostic procedures and has been used for years in fetal monitoring and for many other purposes. There are no needles or ionizing radiation used during this procedure, eliminating the common risks of other diagnostic procedures.