gynecology and obstetrics
Noninvasive Prenatal Fetal Screening Tests
Prenatal Ultrasonography
Most experts recommend Ultrasonography routinely for all pregnant women. Others use ultrasonography only for specific indications, such as checking for suspected genetic or obstetric abnormalities or helping interpret abnormal maternal serum marker levels. If ultrasonography is done by skilled operators, sensitivity for major congenital malformations is high. However, some conditions (eg, oligohydramnios, maternal obesity, fetal position) interfere with obtaining optimal images. Ultrasonography is noninvasive and has no known risks to the woman or fetus. Basic ultrasonographyis done to Confirm gestational age Determine fetal viability Detect a multifetal pregnancy During the second or third trimester, possibly identify major malformations in the fetal intracranial structures, spine, heart, bladder, kidneys, stomach, thorax, abdominal wall, long bones, and umbilical cord Although ultrasonography provides only structural information, some structural abnormalities strongly suggest genetic abnormalities. Multiple malformations may suggest a chromosomal disorder. with high-resolution ultrasonography equipment, is available at certain referral centers and provides more detailed images than basic ultrasonography. This test may be indicated for patients who have or whose partner has a family history of a congenital malformation (eg, Overview of Congenital Cardiovascular Anomalies , Renal malformations (eg, Renal agenesis [Potter syndrome], Lethal forms of short-limbed skeletal dysplasias (eg, thanatophoric skeletal dysplasia, achondrogenesis) Gut malformations (eg, obstruction) Diaphragmatic Hernia None Macrocephaly None Hydrocephalus None Targeted ultrasonography is used to assess risk of chromosomal abnormalities by searching for structural features associated with fetal aneuploidy (so-called soft markers, such as renal pelvis dilation or hyperechoic bowel). However, no structural finding is diagnostic for a given chromosomal abnormality, and all soft markers may also be seen in fetuses that are chromosomally normal. If results from prior trisomy screening were negative, many of these soft markers have no clinical relevance and may be ignored ( Second-trimester screening references ). Nonetheless, the discovery of such a marker may lead to offering the woman 