Objective To correlate prenatal and postnatal findings of all cases of isolated fetal lower limb anomalies, to inform antenatal counselling of parents.

Methods The authors identified all fetuses presenting to the Fetal Medicine Unit at University College London Hospital with a lower limb abnormality between 1995 and 2009. Those with isolated femoral and/or lower leg abnormalities were selected and postnatal findings correlated with prenatal findings.

Results The authors identified 138 fetuses, of which 84 cases had isolated femoral or lower leg abnormalities. Of these 84, 52 had generalised shortening (<third percentile) of all long bones. In the remaining 32 cases there was an apparently isolated lower limb anomaly. The prenatal findings were confirmed after birth in 30 cases, one was lost to follow-up and in one a missing tibia was misdiagnosed as a missing fibula. Of the eight cases with bilateral lesions, a skeletal dysplasia was subsequently diagnosed in the seven cases with symmetrical leg abnormalities. For all cases not associated with an underlying skeletal dysplasia, plotting the size of the affected limbs showed that the growth velocity is usually maintained, albeit along a line below the normal centiles.

Conclusion Prenatal ultrasound can identify with a reasonable degree of accuracy the abnormalities associated with isolated hypoplasia of the lower limb. The data presented here suggest that the initial degree of shortening is maintained throughout the pregnancy allowing a reasonably reliable estimate of size at birth. Fetuses with bilateral, symmetrical lower limb anomalies are more likely to have an underlying skeletal dysplasia.