Usefulness of a short femur in the in utero detection of skeletal dysplasias.

Abstract

In 28 fetuses studied during a 4 1/2-year period, the initial femur was below 2 standard deviations (SDs) of the mean when compared with the biparietal diameter. These fetuses were considered at risk for skeletal dysplasias and were followed up. Studies were performed at a mean gestational age of 26.7 weeks (range, 15.3-41.0 weeks). Group 1 had a femur length 1-4 mm below the 2-SDs line (range, -2.0 to -4.0 SDs); no other abnormalities were detected. Interval examination of 12 femurs showed that 10 either remained shortened to the same degree or had a growth spurt. At birth, all subjects were healthy except one with mild growth retardation and one with a chromosomal abnormality. Of the two subjects that failed to continue normal growth, one was healthy and the other was a heterozygous achondroplastic dwarf. Group 2 had greater femoral shortness; all measurements were more than 5 mm below the 2-SD line (range, -4.3 to -31.0 SDs). All had fetal abnormalities and significant skeletal dysplasias. The authors conclude that the number of millimeters below the 2-SDs line is an accurate, easy criterion for evaluation of femoral length.

Fetal short femur length in the second trimester and the outcome of pregnancy

“…This had already been shown by Kurtz et al 1 who studied 28 fetuses with short FL: 12 had a severe abnormality (FL !5 mm below the 2 SD limit), all with skeletal dysplasias; 16 had a milder abnormality (FL 1 -4 mm below the 2 SD limit), only one of which had heterozygous achondroplasia. However, Kurtz et al's study considered fetuses over a wide range of gestational ages (15 -41 weeks, mean 26), while we restricted our observations to the period of routine midtrimester scanning.…”

Ultrasound Assessment of Biometric Trends in a Case of Thanatophoric Dysplasia

“…A femur length of 2 SD below the mean may also be a sign of severe intrauterine growth retardation [7]. For skeletal dysplasia to be suspected, femur length measurement has to be at least 4 SD below the mean -a cutoff value at which the skeletal disorder is present in all cases [8]. In the case of our patient, a femur length of 5 SD below the mean could be verified already at week 21, confirming the above observations.…”

Midtrimester Isolated Short Femur Length as a Predictor of Adverse Pregnancy Outcome

“…A short FL is variably defined as <5th-10th percentile for gestational age [2,3,4,5,6,7,8,9,10,11,12,13,14,15,16]. It is associated with congenital anomalies [2,3], aneuploidy (mostly trisomy 21) [2,3,6,7,8], skeletal dysplasia [4,5 ]and adverse pregnancy outcome [2,3,9,10,11,12]. Specifically, in the absence of anatomical or chromosomal malformations, isolated short FL has been associated with intrauterine growth restriction (IUGR), being small for gestational age (SGA) [2,3,9,10,11,12,13,14,15]and preeclampsia [11,16].…”