• fetal ultrasonography
• fetal extremities
• clubfoot
• prenatal diagnosis
• ultrasound

Limb anomalies are often missed on prenatal sonography, and this is particularly true with regard to hand or foot defects. It is well known that phalange anomalies can be extremely difficult to diagnose in utero. In a large number of cases these abnormalities are isolated, but they can be frequently associated with other fetal anomalies, for example malformations or chromosomal disorders.
The aim of the present study was to evaluate the accuracy of targeted sonography in detecting and describing limb defects.
We reviewed 80 consecutive pre- and / or post- natal diagnoses of fetal / neonatal deformities of the extremities in pregnant women who had received an ultrasound scan in the referral center of the University of Pisa between January 2002 and May 2017. All cases were reviewed by the clinical geneticist, in order to obtain the appropriate diagnosis selecting the correct genetical tests.
More than half of the limb anomalies were represented by abnormal limb attitude (47 out of 80). In 41 fetuses the abnormal limb attitude was represented by clubfoot / feet, whereas 6 showed an abnormal attitude of all four extremities without any structural or bony malformation.
At neonatal or post-mortem examination, 6 fetuses showed agenesis of one hand (n=5) or both feet (n=1). The remaining cases consisted of various types of finger or toe malformations, such as polydactyly (n=7), syndactyly (n=2) or finger / toe agenesis(n=4), which were for the most part combined together, and were grouped in the present study as “complex” anomalies (n=13).
Overall, limb anomalies affected only the feet more frequently than only the hands (47 vs 16, p < 0.0001); most of them were clubfoot (n=41), associated with neural tube defects in 8 fetuses. Foot anomalies were bilateral more frequently than hand anomalies (26 / 47 vs 4 / 16; p < 0.0001).
Hands and feet were concurrently involved in 16 cases, which mainly consisted in abnormal attitude (6 cases, all forms of arthrogryposis), or “complex” (8 cases).
A syndromic form was diagnosed in 21 fetuses, out of which 9 had a chromosomal anomaly, and 6 cases received a specific diagnosis confirmed by molecular biology. Fetuses with anomalies of both upper and lower extremities had a syndrome more often than fetuses with anomalies of only feet or only hands (11 / 16 vs 10 / 63, p < 0.0001).
Ultrasonographic sensitivity for anomalies of fetal extremities was 79.7%, with a positive predictive value of 98%; the only false positive result was a diagnosis of clubfoot in a fetus spontaneously miscarried at 15 weeks of gestation. On the whole, sonographic anomalies were correctly recognised in 90.5% of fetuses that resulted to have a syndrome at genetic tests, while in nonsyndromic fetuses the percentage of identification was 71.2%. However, the sensitivity varied according to the different anomalies: ultrasound detection was 36 / 41 for clubfoot, 5 / 6 for arthrogryposis, and 6 /
6 for agenesis of the whole extremity. By contrast, 4 cases out of 13 in the group of “complex” anomalies eluded ultrasound prenatal diagnosis.