Fetal biometric ratios by transvaginal sonography as a marker for aneuploidies in early pregnancy.
The aim of this study was to obtain by transvaginal sonography in early pregnancy normal biometric charts of some fetal ratios and to evaluate the utility of these ultrasonographic indices as biometric markers for the identification of fetal chromosome abnormalities. The study population included 1054 normal euploid fetuses and 30 fetuses with an abnormal karyotype. We obtained six standard ultrasound measurements by transvaginal sonography at 11-16 weeks' gestation before genetic amniocentesis in patients at risk for genetic disorders. Seven biometric ratios (biparietal diameter/femur length, biparietal diameter/humerus length, head circumference/abdominal circumference, abdominal circumference/femur length, abdominal circumference/humerus length, femur length/foot length, and humerus length/foot length) were calculated and reference curves were plotted. The ratios from aneuploid fetuses showed no differences from reference ranges. Only in trisomy 13 fetuses were abnormal values of head circumference/abdominal circumference, biparietal diameter/humerus length, and biparietal diameter/femur length ratios detected, probably due to the high incidence of microcephaly and central nervous system malformations in these fetuses. The normal values of sonographic ratios obtained by transvaginal sonography in the first and early second trimester of pregnancy cannot generally be considered a useful tool for the detection of chromosomal abnormalities. Only ratios involving cephalic measurements can be used in early pregnancy as screening markers in the detection of trisomy 13 fetuses.
Guariglia
L
L
Department of Obstetrics and Gynecology, Catholic University of the Sacred Heart, Rome, Italy.
Rosati
P
P
D000782:Aneuploidy; D000886:Anthropometry / Q000379:methods*; D005260:Female; D005333:Fetus / Q000033:anatomy & histology*; D005865:Gestational Age; D006801:Humans; D011247:Pregnancy; D011261:Pregnancy Trimester, First; D011262:Pregnancy Trimester, Second; D016216:Ultrasonography, Prenatal / Q000379:methods*