Abdominal ultrasounds are used in pregnancy to check on the baby and potentially detect concerns with the pregnancy. It is a reliable way to check on a baby's gestational age, growth, detect multiple gestations and establish the placental location. Early identification of problems in the pregnancy can direct medical care for better pregnancy outcomes.
First Trimester
An ultrasound in the first trimester, performed before 13.5 weeks of pregnancy, is used to confirm the viability of the pregnancy and determine the gestational age of the embryo. A standard ultrasound, also called a level I, is generally used. Sometimes, a transvaginal ultrasound is used if the clinician cannot get a good look though the abdomen. The first trimester ultrasound has the ability to detect multiple gestations, ensure that the embryo is not outside the uterus and detect the heartbeat.
Second and Third Trimester
Standard ultrasounds performed in the second and third trimester look at the age and size of the fetus, how many babies are present, where the placenta is located and detect the heartbeat. This evaluation can also determine if the normal amount of amniotic fluid is present and look at the basic fetal anatomy. A second trimester ultrasound usually takes place between 18 and 20 weeks gestation. Woman may or may not have a third trimester ultrasound, depending on the recommendations of her doctor.
Specialized Ultrasound Evaluations
If a potential birth defect is identified, a more detailed ultrasound may be ordered. Called a "level II" ultrasound, the evaluation takes a careful look at the baby's size, head circumference and internal organs--including the heart, stomach and kidneys. The clinician also looks at the length and structure of the arms and leg bones, the spine and the face. Depending on the type of birth defect suspected, more frequent ultrasounds or a 3D/4D ultrasound may be performed. Changes may be made to pregnancy management, the way the baby is delivered and creating a medical care plan for after the baby is born.
Types of Ultrasounds
A standard ultrasound is the most common type. Some practices have a Doppler ultrasound that evaluates blood flow though the baby. This includes blood flow in and out of the umbilical cord. 3D ultrasounds provide a "picture-like" image, unlike a standard, 2D ultrasound that only shows a cross-section of the baby. A 4D ultrasound includes video, allowing a real-time look at the fetus. The 3D and 4D ultrasounds are often used to evaluate specific types of suspected birth defects, such as cleft lip.
Considerations
According to the American College of Obstetricians and Gynecologists, the use of ultrasounds in pregnancy is safe when used appropriately. A certified technician at a reputable center should perform the ultrasound. The American Institute of Ultrasound in Medicine and the American College of Radiology provides certification in the United States. Ultrasound use in pregnancy is considered a screening test and does not often provide diagnostic results.
References
- "Prenatal Diagnosis"; Mark I. Evans; 2006
- "Obstetrics & Gynecology"; ACOG Practice Bulletin No. 101: Ultrasonography in Pregnancy; February 2009
