The genetic sonogram, also called a targeted sonogram or Level II sonogram, is performed at 15 to 22 weeks into the pregnancy. This ultrasound scan includes an examination of the developing fetus, the uterus, placenta, cervix and the regions of the ovaries.
At the 15- to 22-week mark in the pregnancy, measurements should match within 10 days of the actual pregnancy dating. If there is a discrepancy, then unless an ultrasound was done earlier that confirmed the dates, we will recommend re-dating the pregnancy based on the scan.
At 15 to 22 weeks, we perform a detailed evaluation for abnormalities of the baby, including a comprehensive look at the structures of the developing brain, the face, lips, nose and profile, and also the spine, heart, abdomen, kidneys, bladder, extremities and umbilical cord. More than 90 percent of the time, we are also able to determine baby’s sex at 15 to 22 weeks into the pregnancy.
There are some situations – for example, a difficult position of the baby, abdominal wall scarring from prior surgeries or irregularities of the uterus – that will prevent us from being able to see the baby’s sex this early. Many parents ask us to take a guess. We won’t! Our goal is to have 100 percent accuracy in sex determination for you.
About 1 percent of all babies have a major structural malformation, ranging from abnormalities of the brain, spine, heart, kidneys, or extremities. Our center has been performing genetic sonography for more than 20 years, and we have had experience in the diagnosis of thousands of birth defects. Our goal is to identify more than 75 percent of major structural malformations by 22 weeks.
Why can’t we see all of all major structural malformations? Sometimes, there will be limitations based on early stage in the pregnancy, scarring of the abdominal wall or the uterus, or the position of the fetus. In these cases, we may recommend a repeat sonogram. But even if we are able to obtain clear views of the fetus, it is important to realize some structural malformations have not happened by 22 weeks. These include abnormalities of the brain and heart. Other malformations, even some that are very obvious in looking at the newborn, cannot be clearly identified on scan. If there is a specific concern that you have, please let us know, and we can tell you whether your scan has excluded the possibility of the birth defect you are concerned about.