Ultrasonographic prediction of fetal outcome in suspected skeletal dysplasias with use of the femur length-to-abdominal circumference ratio.
OBJECTIVE
Our purpose was to determine whether the femur length-to-abdominal circumference ratio can be used antenatally to predict a lethal skeletal dysplasia.


METHODS
All obstetric sonograms performed from January 1990 to October 1995 were reviewed (44,020 studies) to find those scans suggestive of a skeletal dysplasia. Thirty patients were identified. The femur length/abdominal circumference ratio was then calculated from each patient's initial and subsequent sonograms. Birth outcomes were obtained on the 27 patients who elected to continue their pregnancies.


RESULTS
All fetuses with a lethal skeletal dysplasia (n = 12) had a ratio <0.16. The fetuses with a nonlethal dysplasia (n = 8) had ratios between 0.134 and 0.193, with only 1 fetus with a ratio <0.16. All fetuses with no evidence of a skeletal dysplasia after birth (n = 7) had femur length/abdominal circumference ratios >0.18. The 1 fetus with a ratio <0.16 who survived the neonatal period had extreme bowing and demonstrates the limitation of the ratio when bowing is present.


CONCLUSIONS
A stillbirth or neonatal death occurred in 12 of 13 patients with a femur length/abdominal circumference ratio <0.16, independent of gestational age. Conversely, no fetus with a ratio >0.16 was found to have a lethal skeletal dysplasia. This information may be useful in counseling women when ultrasonography suggests the diagnosis of a skeletal dysplasia.
Ramus
R M
RM
Departments of Obstetrics and Gynecology and Radiology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
Martin
L B
LB
Twickler
D M
DM
D000005:Abdomen / Q000000981:diagnostic imaging*; D001848:Bone Diseases, Developmental / Q000000981:diagnostic imaging* / Q000401:mortality; D005260:Female; D005269:Femur / Q000000981:diagnostic imaging*; D005313:Fetal Death / Q000453:epidemiology; D005544:Forecasting; D006801:Humans; D015994:Incidence; D007226:Infant Mortality; D007231:Infant, Newborn; D011247:Pregnancy; D011256:Pregnancy Outcome; D011859:Radiography; D016216:Ultrasonography, Prenatal