Association of isolated short fetal femur with intrauterine growth restriction

Objectives: To analyze the outcomes of fetuses referred because of short femur length. Methods: This was a retrospective study of all singleton pregnancies referred to a tertiary care referral hospital with a femur length below the 5^th percentile. All ultrasound scan reports, including Doppler, fetal karyotyping, pregnancy outcome and neonatal data were analyzed. Results: In 112 patients, 87 (78%) had an isolated short femur and 25 (22%) had a non-isolated short femur. The non-isolated cases consisted of chromosomal disorders (n=6), skeletal abnormalities (n=6), multiple abnormalities (n=12) and 1 genetic disorder. In the isolated group 37 cases (43%) were intrauterine growth restricted (positive likelihood ratio 1.20, negative likelihood ratio 0.45). In 33 cases the short femur was unexplained and 17 referrals were considered false-positive. The growth restricted group had significant more abnormal Doppler measurements (p=0.01), caesarean deliveries (p=0.043) and admissions to the neonatal intensive care unit (p=0.001). Conclusion: An isolated short femur is associated with intrauterine growth restriction and adverse pregnancy outcome.