Pregnancy UltrasoundAn obstetric, or pregnancy, ultrasound examination is performed to image the fetus and surrounding pelvic structures. Ultrasound produces images of the body’s internal organs. Ultrasound is most often performed in the first trimester of pregnancy.
During the first trimester of pregnancy, an obstetric ultrasound examination is performed to image the fetus and surrounding pelvic structures. Typically, an ultrasound performed early in the pregnancy is done to confirm a normal pregnancy, determine the baby's age, check the baby's heart rate, look for multiple pregnancies and identify any concerns such as ectopic pregnancies or the chances for a miscarriage.
An OB Ultrasound examination will be performed by a technologist who is an expert in using ultrasound. A hypo-allergenic, water-soluble gel will be applied to your lower abdomen to prevent air from getting between the ultrasound source and your skin. A small probe, called a transducer, will be passed over the surface of your lower abdomen, producing a painless sensation of light pressure on your skin. The exam typically takes about 45 minutes and requires your bladder to be full.
A Transvaginal Ultrasound examination may also be required during the first-trimester of pregnancy. After you empty your bladder you will be asked to insert a tampon-shaped transducer a short distance into your vagina. This procedure images the uterus, fetus and pelvic structures more closely.
A pregnancy ultrasound may also be done in the second and third trimesters to confirm the baby’s age, growth, position and gender as well as to identify any developmental problems. The radiologist could also be checking for any development problems.
RAS also performs a special prenatal scan to help identify higher risks of chromosomal defects in a fetus. This is particularly useful for older women who have higher risks of such pregnancies. The scan assesses the thickness of soft tissues of the nape of neck of the fetus - also known as the nuchal fold. This diagnostic test, called Nuchal Translucency (NT) ultrasound, is commonly used to look for signs of Down syndrome or other developmental problems in the developing baby. The results are combined with blood tests, usually obtained by a perinatologist. The NT scan must be done when a woman is between 11 and 14 weeks pregnant, because this is when the base of the baby's neck is still transparent. Babies with abnormalities tend to accumulate more fluid at the back of their neck during the first trimester, causing this clear space to be larger than average.
In order to fill your bladder for an OB ultrasound, you must drink 16 ounces of water one and half hours before the ultrasound is performed. This amount of time is sufficient for the water to go through your system and enter your bladder. If your bladder is not full enough for this examination, your appointment may need to be rescheduled.