Fetal biometry as a screening tool for the detection of chromosomally abnormal pregnancies.
Recent studies suggest that fetal biometry may allow recognition of pregnancies at risk for Down syndrome. Second-trimester biparietal diameter (BPD)/femur length and observed-to-expected femur length ratios were examined in 48 chromosomally abnormal fetuses and compared with those of a control population composed of both low-risk patients (maternal age less than 35 years) and high-risk patients (maternal age 35 years or more). Biparietal diameter/femur length ratio correctly identified 18% of Down syndrome pregnancies with a positive predictive value of one in 169 and a false-positive rate of only 4%. When trisomies 21, 18, and 13 were considered collectively, a sensitivity of 29% and a predictive value of one in 78 were achieved, with no increase in the false-positive rate (4%). Observed-to-expected femur length ratio was less valuable in detecting chromosomally abnormal fetuses. These data suggest that the BPD/femur length ratio holds promise as a screening tool for the antenatal detection of fetal chromosomal abnormalities. Although encouraging, extrapolation of these results to other centers is not recommended without independent verification.
Dicke
J M
JM
Department of Obstetrics and Gynecology, Washington University School of Medicine, Jewish Hospital, St. Louis, Missouri.
Gray
D L
DL
Songster
G S
GS
Crane
J P
JP
D001699:Biometry; D002869:Chromosome Aberrations / Q000175:diagnosis; D025063:Chromosome Disorders; D004314:Down Syndrome / Q000175:diagnosis*; D005260:Female; D005315:Fetal Diseases / Q000175:diagnosis*; D005333:Fetus / Q000033:anatomy & histology*; D006801:Humans; D008423:Maternal Age; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D011296:Prenatal Diagnosis / Q000379:methods*; D012016:Reference Values; D014463:Ultrasonography