Outcome of fetuses with antenatally diagnosed short femur.

OBJECTIVES

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

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.