Ultrasounds use sound waves to produce an image so doctors can observe fetal growth and development. Doctors rely on pregnancy ultrasounds to estimate fetal age, as well as the locations of the fetus and the placenta inside the uterus. Doctors also use ultrasounds to confirm the number of fetuses present and to record heart rate. Later in pregnancy, ultrasounds can even detect some birth defects, such as club foot or cleft palate.
A hand-held instrument called a transducer directs sound waves into the abdominal or pelvic cavity. Mineral oil or another gel-like substance creates a barrier between the skin and transducer to eliminate air pockets which might disrupt the image. The sound waves hit tissues, organs, bones and fluid, and then bounce back to convey the image on a monitor. Dark areas show liquid, such as amniotic fluid, and white or gray areas reflect denser matter.
Many women have a transvaginal or transabdominal real-time ultrasound at some point in their pregnancy. A real-time ultrasound pieces together many still frames to create a moving image. Transabdominal refers to where the doctor places the transducer on the abdomen. During a transvaginal ultrasound, the doctor covers a wand-like transducer with latex and gel then inserts it into the vagina. This type of ultrasound provides a closer look at the mother’s organs and fetus. Most women are familiar with the Doppler ultrasound, which is what doctors use to listen to the fetus’s heartbeat. If a doctor suspects a problem with the baby’s heart, she will perform a fetal cardiogram using either the transvaginal or transabdominal method. Doctors perform a sonohysterography in conjunction with the transvaginal ultrasound. A catheter is placed inside the cervix and then injected with a saline solution. The uterus expands to make it easier for the doctor to detect abnormalities. Three- and 4-D ultrasounds are similar in that they use thousands of images to create a more lifelike representation of the fetus. Four-dimensional ultrasounds also show fetal movement.
According to the American Pregnancy Association, doctors can perform ultrasounds at any point in pregnancy. However, doctors do not typically use ultrasound unless it’s medically necessary. Of all the ultrasound methods, doctors use the transvaginal early in pregnancy to obtain a more accurate depiction of fetal size and gestational age.
In preparation for a transabdominal ultrasound, the patient should wear loose clothing so that she can easily expose her belly. Some doctors might suggest coming to the appointment with a full bladder. A full bladder pushes the intestines out of the way and uterus higher into the abdominal cavity so that the images are clearer. The doctor then applies a gel to the abdomen and uses the transducer to perform the ultrasound. A transvaginal ultrasound is similar to a pelvic exam. The patient either changes into a gown or undresses from the waist down. She then lies back on the exam table and puts her feet into stirrups, and the doctor inserts the transducer wand into the vagina.
Many women worry about ultrasound safety during pregnancy. Dr. Douglas W. Laube, president of the American Congress of Obstetricians and Gynecologists explains pregnancy ultrasounds do not use any radiation. Furthermore, they do not use a contrasting media, such as a dye, or require patient sedation. Parents-to-be should consider avoiding the companies that promise 3-D and 4-D keepsake pictures and videos. As reported by the American Institute Of Ultrasound In Medicine, the U.S. Food and Drug Administration has not approved ultrasound devices to be used for any reasons other than medical or without a physician’s order.
- pregnant belly button image by davidcrehner from Fotolia.com