Ultrasound technology is an amazing tool that gives us the opportunity to see the living fetus. For parents expecting a child, it provides a thrilling glimpse at the child they’re preparing to bring into the world.
This wasn’t always an option. While it was invented in 1958, the use of sonographic images of the fetus in utero only became a regular phenomenon in the mid-1980s, when computers were becoming commonplace. Before ultrasound was in regular use, physicians could only assess the health of a pregnancy with their clinical examination skills, lab tests and a funny looking stethoscope called a fetoscope.
In the last 30 years, technology has expanded by leaps and bounds, and now the quality of ultrasound images is excellent. We can even get three-dimensional images of the growing fetus.
Now that we have this technology, shouldn’t we be using it all the time? Why not get ultrasounds at every visit? There are questions as to what harm, if any, frequent ultrasounds pose to the health of the child.
Ultrasound through the stages of pregnancy
Ultrasonic images are obtained by transmitting sound waves through tissue and collecting the echoes as they return to the transducer. As a woman moves through the stages of pregnancy, ultrasounds provide very important information for assessing the health and developmental progress of the baby.
Early in the pregnancy, an ultrasound can be used to determine whether a patient is pregnant and get an accurate gestational age. An accurate gestational age is crucial because decisions about the pregnancy after 20 weeks are determined by the week of gestation. Earlier ultrasounds give us more accurate dates.
Because the fetal heart begins beating by six weeks, an ultrasound can tell us whether a pregnancy is developing appropriately.
If a patient is bleeding in the first trimester of pregnancy, an ultrasound can help us diagnose whether the bleeding is benign, or whether it is due to a miscarriage or abnormality. It is not uncommon for a patient to come in for their 12-week visit and need an ultrasound because the doppler is unable to hear the fetal heartbeat. Although dopplers are helpful, at 12 weeks, the fetal heart is only 5-6mm in size and can be difficult to find.
Between 17 and 22 weeks, we often do an ultrasound assessment of the fetus to look closely at the anatomy. This scan can tell us whether the brain is developed appropriately, whether there is a cleft lip, a cardiac abnormality and of course, the gender of the fetus.
This study can also show us whether the fetus is growing appropriately and producing enough amniotic fluid. We also look at the placenta to make sure it is not covering the cervix (placenta previa) and we measure the cervix to make sure it is not abnormally short. These findings can help us decide whether additional ultrasound studies are needed, or whether the delivery needs to occur surgically.
Monitoring for risk
There are certain medical conditions that can put the fetus at risk, such as maternal high blood pressure, Type 1 diabetes and cholestasis of pregnancy (among many others). In these cases, we use a weekly sonogram to evaluate the fetal well-being and the amniotic fluid level.
Related: Your guide to high-risk pregnancy
We also keep an eye on the growth every three to four weeks to make sure that the placenta is continuing to function in providing the nutrients needed for the fetus to grow.
When the fetus reaches a certain age, an abnormal ultrasound may mean that it is time to deliver because the risk of fetal loss is greater if the baby remains dependent on the placenta for survival.
While there has not been any data to suggest that ultrasound is harmful to the baby or mother, there are some who are concerned about the unknown effects that sonographic waves have on a growing fetus. Because of this unknown, and the limited benefit of routine ultrasounds, there is no need to have an ultrasound at every visit.
At the end of the day, an ultrasound provides valuable insight into the various stages of pregnancy, helping physicians and mothers-to-be make healthy and informed decisions on the birth of the child. Find an OB/GYN near you to guide you through your pregnancy.
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About the author
Adrianne Browning, MD, is an obstetrician/gynecologist on the medical staff at Baylor University Medical Center. She received her medical degree at University of Texas Southwestern Medical School and has been a recipient of awards and a member of several prestigious committees over the course of her career. After nearly seven years as a hospitalist at Baylor University Medical Center, she is now a member of a private practice in HTPN, BSWH Women’s Health Group.