Outcome of fetuses with antenatally diagnosed short femur

To examine the outcome of fetuses diagnosed with short femur length at the time of the routine anomaly scan.

This was a retrospective review of all pregnancies referred to a tertiary referral unit with fetal femur length below the 5(th) centile for gestation at 18-24 weeks of gestation. All patients had undergone pregnancy dating and assessment of the risk of chromosomal abnormalities by measurement of fetal nuchal translucency at 11 to 13 + 6 weeks.

Over 5 years, 129 cases were evaluated. Detailed ultrasound examination showed associated fetal abnormalities in 46 (36%) cases, and these were classified as non-isolated. In this group, skeletal dysplasias (n = 16), chromosomal abnormalities (n = 10) and genetic syndromes (n = 4) were the most common associations. In contrast, there were no cases of chromosomal abnormalities or skeletal dysplasia in the 83 (64%) isolated cases. Early severe intrauterine growth restriction (IUGR) with abnormal umbilical artery Doppler findings and delivery before 37 weeks occurred in 33/83 (40%) cases with isolated short femur, and 90% of these had abnormal uterine artery Doppler findings at the time of presentation. These pregnancies also had high rates of pre-eclampsia (36%) and intrauterine death (33%). Those with normal uterine artery Doppler imaging were at low risk for these complications.

In a population previously screened by first-trimester fetal nuchal translucency measurement, the finding of isolated short femur at 18-24 weeks is unlikely to be due to aneuploidy. Severe IUGR associated with high mortality occurs in 40%, making uterine artery Doppler evaluation a useful clinical tool.