**4. Second-trimester assessment**

club or claw hand, and digital defects. The correct diagnosis was made in the majority of cases of a missing hand or foot (77.8%), or polydactyly (60%), and half of the lethal skeletal dysplasia (50%) and isolated shortening of one of the long bones (50%). The only case of ectrodactyly was missed, and arthrogryposis was not suspected during the

**Figure 3.** The whole fetus, imaged by 3D static ultrasound (surface rendering mode). The harmonious development and

relationship between limbs' segments are easy to asses.

**Figure 1.** Normal aspects of fetal hand in the late first trimester.

**Figure 2.** Normal aspects of fetal foot in the late first trimester.

first-trimester scan.

312 Congenital Anomalies - From the Embryo to the Neonate

Most of the authors agree that the fetal anatomy may readily be assessed at 20–24 WG, because:


Some important studies underlined a statistically significant difference being able to perform a complete fetal morphology scan if US is performed at 18 to 19 + 6 (in 76% of cases) versus 20 to 22 + 6 weeks of gestation (in 90% of cases) [21–24]. However, with the improved technological capabilities of the ultrasound equipment, the gestational age for confidently assessment is constantly lowering. On the other hand, due to absorption of sound phenomenon, the visualization of the skeleton is easier than for other fetal systems (e.g., the cardiovascular system). Also, the skeletal system is already completely developed, unlike other structures (e.g., central nervous system components, as the corpus callosum or vermis). Therefore, the fetal skeletal evaluation may be proposed and successfully performed in the routine early second-trimester scan (**Figures 4**–**7**).

**Figure 4.** 2D conventional US images of normal feet at 17 weeks of amenorrhea (WA) and at 23 WA. The normal position of the toe is readily observed. In many cases, numbering the digits is possible.

• the fetal position is maintained for longer periods, due to the reduced mobility;

• the amniotic fluid volume decreases, especially at term; and

movements, as part of the Manning classical biophysical profile.

formations were also located distally (hand and fingers).

tained toward the fetal axis;

**6. Literature**

• the limb's segments have a complete flexion, and the proximal limb's position is main-

The Antenatal Detection of Fetal Limb Anomalies http://dx.doi.org/10.5772/intechopen.76108 315

• the bone ossification increases, impairing the visualization of the underlying structures.

the third trimester. The commendation is stronger if such conditions are suspected.

In certain cases, in the late second and third trimester, the secondary anatomy changes due to functional disturbances (some forms of skeletal dysplasia, fetal tumors, segmental deformations secondary to compression in oligohydramnios, multiple pregnancies, or other pathologies) become evident. Thus, even in cases with a normal morphological examination in the second trimester, the examination of the upper and lower members should be attempted in

In the third trimester, the evaluation of the fetal well-being includes the limbs and hand

Historically, the sensitivity of prenatal ultrasound for detection of musculoskeletal and limb anomalies has been low. In 1991, Levi published a series of 16,072 pregnant women with prenatal ultrasound and found a 45.32% sensitivity for detection of any type of anomaly, with a 23.26% sensitivity for detection of limb and skeletal anomalies [25]. In 1992, Stoll found a 15% sensitivity for isolated anomalies and 48% sensitivity for multiple anomalies for the second-trimester prenatal ultrasounds [26]. The most meaningful result of these early studies is the high specificity of scanning in terms of skeletal abnormalities [25, 26]. This is important, because conditions with high false-positive rates can mislead parents and clinicians in their decisions and recommendations.

Detection of major anomalies has improved over time as a result of improvements in technology and skills, although detection of limb anomalies remained low. The Eurofetus study, in 1999, showed an overall sensitivity for detection of any anomaly to be 61%, with identification of musculoskeletal anomalies much lower and similar to the findings of Levi et al. at 18% [27]. It seems that detection of proximal limb reduction defects is better (23–50%) than detection of hand or finger limb reduction defects (0–8%) [28]. The 2005 EUROCAT study of 4366 fetuses with different anomalies reported a prenatal detection rate for both upper and lower limb reduction defects of 34% [29]. In a more recent study, a higher prenatal detection rate was found for limb reduction defects with associated malformations (49%), if compared to isolated limb reduction defects (25%) [30]. Pajkrt et al. also found a high detection rate for fetuses with short or absent radii and/or ulnae associated with aneuploidy or genetic syndromes (70%) [31]. In another large study, Gray et al. found that 31% of upper extremity anomalies were detected prenatally; however, only 18% were correctly diagnosed [32]. The missed mal-

The difficulties in detection of upper extremity anomalies may be related to the current guidelines. They mandate only a cursory examination of the upper and lower limbs during the standard second-trimester (ST) examination. This may contribute to the high false-negative rate [33].

**Figure 5.** 2D conventional US images of normal fetal hands in midtrimester. Similarly, numbering the fingers is possible and, in certain cases, even the phalanges. As seen, in most cases, the thumb lies in a different plane than the other four fingers. Due to hand anatomy, thumb visualization may not be simultaneous than the other fingers. Yet, confirming the presence of the opposable finger is considered important, due to the prehension function of the hand.

**Figure 6.** Hands and foot, imaged by 3D static ultrasound (surface rendering mode). Using this technique, the demonstration of the extremities is easier, despite the different spatial arrangement of the thumb.

**Figure 7.** Hand imaged by 3D static ultrasound (skeletal mode). The technique makes the confirmation of the normal number of phalanges of each finger easier.
