**7. Technique**

The standard examination includes measurements of fetal biometry, in order to estimate the gestational age and fetal weight. It includes the biparietal diameter (BPD), the head circumference (HC), the abdominal circumference (AC), and the femur length (FL) [34]. The measurements of the humerus length (HL) and the transcerebellar diameter (TCD) are optional in many settings. Yet, the fetal biometry may be completed with other segment measurements, as Jeanty proposed over three decades ago [35]. Benefits of such an approach are investigated recently [36]. For almost all fetal structures, nomograms were created, in order to accurately estimate the gestational age.

In amniotic band syndrome, fingers can be missing. This is due to the arrest in development

The Antenatal Detection of Fetal Limb Anomalies http://dx.doi.org/10.5772/intechopen.76108 317

In some rare syndromes such as ectrodactyly-ectodermal dysplasia-cleft syndrome (EEC syndrome), missing fingers occur in association with complex malformations. EEC syndrome is a rare form of ectodermal dysplasia. It is an autosomal dominant disorder, inherited as a genetic trait. EEC includes also vesicoureteral reflux, recurrent urinary tract infections, obstruction of the nasolacrimal duct, decreased pigmentation of the hair and skin, missing or abnormal teeth, enamel hypoplasia, absent punctae in the lower eyelids, and photophobia. Occasional,

In the development of fetal limbs the free movement itself has a very important role. This is favored by the proximity of fluid in the uterine cavity. The limbs should move freely within each joint. Normal movement assures the normal positions of the hip, knee, elbow, ankle, and wrist joints.

Apparition of abnormal angulation of the ankle joint (ankle clubbing, talipes equinovarus) is frequent, with a prevalence of 1 in 100 live births. The best image is to get a coronal section of the ankle, in which the extended ankle straight along is seen, in a normal spatial relationship with the lower leg. In ankle clubbing, the ankle deviates medially. In the third trimester, especially when the amniotic fluid decreases, a slight subjective angulation of the ankle is common. The key feature for ruling out a true clubbing is the normal shape of the foot. Unilateral ankle clubbing is usually an isolated defect. Bilateral clubbing should be investi-

The wrist is very flexible and the position of the fingers is also variable. Thus, the examination can find them in a wide variety of positions. In late second trimester and third trimester, the resting position is fisting. The hand can be stimulated to open, showing all four fingers and the thumb. Due to the anatomy of the hand, the thumb is visible in a different plane from the rest of the fingers. Due to this particular context, the diagnosis of abnormal hand position is

All limb anomalies, other than isolated polydactyly, have an increased risk for associated nonskeletal malformations, aneuploidy, stillbirth, neonatal neurodevelopmental delay, and pregnancy termination [43]. This information influences the guiding of evaluation and man-

The abnormal number of fingers or abnormal position of fingers (Campylodactyly or clinod-

The shortening of the humerus seems to have a slightly better predictive value than shorten-

In skeletal dysplasias, the shortening or fracture of long bones is a criterion for diagnosis. The site and the type of shortening are important in establishing an accurate diagnosis (**Table 2**).

cognitive impairment, kidney anomalies, and conductive hearing loss may appear.

and not as a primary defect in the blastulation process.

gated for chromosomal anomalies and genetic syndromes.

agement, the counseling of parents, and the delivery planning.

actyly) is associated with an increased risk of an underlying fetal syndrome. An image of "sandal gap" anomaly has a weak association with trisomy 21.

ing of the femur in screening for aneuploidies, especially for trisomy 21.

more difficult than in distal limb.

**9. Rationale of screening**

For limbs examination is recommended to start the sweep proximally. The long bones must be measured in their entirety ("end to end") in a parallel plane to the probe. The examination aims to confirm the normal mineralization and the absence of fractures. The "shortening" diagnosis is allowed only if a previous scan certifies gestational age (preferably, a first-trimester scan).

The forearm and lower leg contain two long bones. In routine examination their presence and normality should be confirmed. If differences between them are suspected or in the presence of other anomalies, all measurements and comparison with the standard data for the gestational age should be done. At the elbow, the ulna is located medially to the radius and has a much higher extremity in relation with humerus. At the wrist, its position depends on the degree of rotation of the forearm.

The image of the foot is obtained in a transverse section to show the heel, the sole, and toes. The position of the big toe with respect to the other toes can be evaluated readily. The length of the foot is not a part of the routine examination, but is important in assessment of skeletal dysplasias and in cases of short femur. If the dimensions of foot remain in normal range for the gestational age and the femur is short, the femur/foot length ratio will be significantly decreased (0.9). In fetuses with constitutionally short femur, this ratio will remain normal.

The ideal window for visualizing the fetal hands is at the late first and early second trimester, when the fingers tend to be extended and abducted. US examinations will be less accurate later in pregnancy, due to fetal position and flexed digits [37]. By some authors, the use of three-dimensional (3D) and 4D US, as well as fetal MRI, improves detection of hand anomalies [32, 37–42]. However, the technique is not currently recommended for routine use by The American College of Obstetricians and Gynecologists [3, 33].
