Ultrasound in pregnancy has been used since the 1970s. It is the process of using sound waves reflected from a tissue interface within the body, such as the fetus, back to the ultrasound transducer which produces an image on the screen. OB Ultrasounds do not shine a light on the baby and do not use any radiation.
We perform almost all of our OB ultrasounds in our office for your convenience and quick results for your doctor. All ultrasound scans are performed by our ARDMS registered Ultrasound technologist or your doctor.
We use ultrasound during pregnancy for various reasons. Most common reasons are:
- Pregnancy Dating
- Confirmation of pregnancy
- Fetal Growth and Anatomy
- Fetal Viability
- Fetal Presentation
- Evaluate Amniotic Fluid Levels
- Placenta Location
- Twin Gestation
- High-Risk Situations
Early OB Scans
Early OB scans are done for confirmation of pregnancy; to detect the small fetus, yolk sac, and gestational sac; and for a fetal heart rate, which can, in most cases, be detected as early as 5 weeks and 4 days of pregnancy. We can also determine twin or single gestation, location, and confirm that the pregnancy is within the uterine cavity. Early ultrasounds are also used in cases of vaginal bleeding or spotting during your pregnancy.
By approximately 7 to 13 weeks in pregnancy, we can easily measure the “crown-rump”, or the length of your baby from the top of the head to the baby’s bottom. This gives us a very accurate dating of your pregnancy within 3 to 4 days of your LMP date. The earlier the scan is performed, from about 7 weeks forward, the more accurate is the fetal measurement (until about 18 to 20 weeks).
By approximately 9 weeks, a small fetus can be seen with separate head and abdomen, and usually, limb buds and umbilical cord are also visible. Fetal gender is difficult to determine before about 20 weeks gestation and gets easier as the pregnancy progresses from there. As baby grows larger, gender is more easily seen and confirmation is more accurate.
20 Week Scan (size and dates)
When your doctor orders your 20 week (size and dates) scan, sometimes referred to as a “level 2″ scan, we no longer measure the “crown-rump” length but measure fetal head, abdomen, and femur (thigh). Your 20-week scan is sometimes all that is needed during your pregnancy. At this time, we perform a complete scan of your baby in our office, documenting fetal anatomy, including fetal heart, limbs, and brain. We can usually also determine gender should you desire. Assessment of fetal growth is done at this time. Fetal measurements can give us an approximate weight of your baby. Approximately 90% or more of all fetal abnormalities can be reliably diagnosed with a 20-week scan; and, steps can be taken if indicated, for intervention before or at the time of baby’s birth.
Ultrasound is used in twin or multiple gestation pregnancies to determine the number of fetuses, identical or paternal, and follow their growth.
Other OB Ultrasound Procedures
Ultrasound is also used to assess the location and evaluation of the placenta, cord, uterus and ovaries, amniotic fluid, fetal presentation, fetal movements, and many other high-risk reasons your doctor may wish to evaluate.
3 Dimensional Ultrasound can be used along with your regular 2D ultrasound exam for many reasons as determined by your doctor or technologist. It can sometimes help in the evaluation of certain fetal structures. 4D is the process of 3-dimensional scanning and watching the baby move at the same time. Our office is fully equipped with this technology. See our 4D Memories page for more information on a 4D imaging opportunity for you and your family.