**9. Rationale of screening**

**7. Technique**

316 Congenital Anomalies - From the Embryo to the Neonate

degree of rotation of the forearm.

**8. Types of limb abnormalities**

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. 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

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

The most common types of limb anomalies include abnormal number of digits (the higher frequency having polydactyly), abnormal hand/foot position, limb reduction defects, and

Abnormal hand position is defined as clenched hands or overlapping digits. Arthrogryposis

Counting the fingers is not part of routine scan. Polydactyly is more common in some ethnic groups, such as African Americans. It may occur isolated or may affect both hands and feet.

American College of Obstetricians and Gynecologists [3, 33].

arthrogryposis. It seems that unilateral limb defects are rarer.

is defined as fetal joint contractures and rigidity.

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

The abnormal number of fingers or abnormal position of fingers (Campylodactyly or clinodactyly) is associated with an increased risk of an underlying fetal syndrome.

An image of "sandal gap" anomaly has a weak association with trisomy 21.

The shortening of the humerus seems to have a slightly better predictive value than shortening of the femur in screening for aneuploidies, especially for trisomy 21.

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**).


\* The term does not include the malformation, fractures, or absence of the bones.

\*\*Normal measurements is related to an accurate gestational age, ideally established in the first trimester of pregnancy.

**Table 2.** Terminology in long bone abnormalities.

The upper limb anomalies (and especially radial hypoplasia or aplasia) are phenotypical features of a number of syndromes.

**Figure 9.** 3D ultrasound images (surface rendering mode), applied in a case of polydactyly. The case was scanned in the

The Antenatal Detection of Fetal Limb Anomalies http://dx.doi.org/10.5772/intechopen.76108 319

**Figure 10.** 3D ultrasound images (surface rendering mode), applied in cases of polydactyly in the second trimester; the volume datasets were acquired by means of transabdominal scan. The images were used in the parental counseling process.

**Figure 12.** Unilateral postaxial polydactyly type I. Different techniques for acquiring the 3D volume datasets: surface rendering, skeletal mode, and HD life. The case evolved with spontaneous amputation in utero (reproduced with

**Figure 11.** Ectrodactyly: conventional 2D ultrasound, 3D ultrasound skeletal mode, and pathological specimen correlated.

permission of authors) [39].

first trimester, and the volume was acquired by means of transvaginal scan.

The primary advantage of prenatal diagnosis of upper extremity anomalies is the opportunity for more refined prenatal counseling [44]. Parents are given the chance to discuss their child's diagnosis with a variety of specialists and to receive genetic counseling. For treatable anomalies, a team may be assembled to prepare for postnatal care. Some families will consider pregnancy termination for major untreatable anomalies, and several studies have shown higher rates of pregnancy termination after early prenatal diagnosis of major untreatable anomalies [25, 28, 29, 45].
