Prospective parents often leave their obstetrician’s office after the second trimester ultrasound with a grainy black and white image, a glimpse of their developing baby’s nose, fingers, or feet.
Maternal fetal medicine specialists in CUMC’s Department of OBGYN perform dozens of these fetal anatomic surveys every week. Most of them reveal a normally developing fetus, with everything as it should be. But since CUMC’s Center for Prenatal Pediatrics (CPP) is a referral center for pregnancies with fetal complications, Karin Fuchs, MD, OBGYN’s director of ultrasound, and her colleagues see several patients every day who have already been diagnosed with a fetal structural malformations at another center. “A substantial part of our practice is prenatal diagnosis,” says Dr. Fuchs, “and significant proportion of what we see are complex cases.”
Obstetricians use ultrasound early in a pregnancy to confirm the number of fetuses, the gestational age, and to do a preliminary assessment of genetic and anatomic risks. During the second trimester they perform an anatomic survey, examining the fetus from head to toe for major structural abnormalities or genetic, infectious, or growth disorders that might increase the risk of complications.
“A substantial part of our practice is prenatal diagnosis,” says Dr. Fuchs, “and significant proportion of what we see are complex cases.”
Major fetal structural malformations occur in 2 to 3 percent of pregnancies, according to Dr. Fuchs, and about a third of these anomalies are a form of congenital heart disease. Other less common anomalies include spina bifida, diaphragmatic hernias (a hole in the diaphragm between the chest and the belly), or defects of the abdominal wall (omphalocele and gastroschisis). “We also see malformations such as clubbed feet or cleft lip, which are clearly very important to parents, but are generally not life-threatening anomalies,” she says.
During a standard ultrasound, sound waves are used to create a 2D image in shades of black and white. In contrast, 3D ultrasound uses additional software to create an image that is far more lifelike than 2D, showing depth and texture of structures. 3D ultrasound enables doctors to create renderings of fetal surfaces that can be particularly useful in the evaluation of masses and defects in the fetal abdominal wall or spine. “3D ultrasound enables us to assess the spatial relationships of structures, and, if we do find an abnormality, can help patients visualize the malformation and understand its significance,” Dr. Fuchs says.
Read more about 3D ultrasounds in the current issue of Connections.