**9. Extremities**

Congenital malformations of the extremities may appear as solitaire anomalies or as multiplex abnormalities associated with syndromes. Most of these malformations are hard to diagnose prenatally, the sensitivity of ultrasound is around 25% [50, 51]. Measurements of the length of the femur and the humerus are part of the fetal biometry [52, 53].

When the placenta is abnormally attached, it may reach the myometrium (placenta accreta), the serosa (placenta increta) or other organs (placenta percreta). The detection of placenta accreta is hard, but increta and percreta are easier to visualize. The birth prevalence of pla-

Congenital Fetal Anomalies and the Role of Prenatal Ultrasound

http://dx.doi.org/10.5772/intechopen.71907

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The maturity of the placenta was classified by Grannum in 1988 based on the ultrasound image:

centa accreta is 1:2500, while in placenta praevia cases, the prevalence is 1:10 [56, 57].

• Grade 0: First two trimesters, the chorionic plate is smooth, uniform echogenicity • Grade I: 18–29 weeks, indentations of the chorionic plate, occasional echodensities

• Grade III: after 36 weeks, complete indentations, large echodense areas, calcification

When the maturity of the placenta and the fetal biometry are discordant, it suggests intrauter-

Examination of the insertion site of the umbilical cord is also important as it provides the nutrient supply going to the fetus. Marginal insertion is often associated with intrauterine growth retardation. In case of velamentous cord insertion, the umbilical vessels are only covered by the amniotic membrane, therefore they are less protected. Also, this anomaly is often associated with the presence of a single umbilical artery [57]. Single umbilical artery is present in 0.2–1% of the pregnancies. It is a minor anomaly that is often associated with cardiovascular,

Normally, the umbilical cord is 50 cm long at terminus. When it is shorter than 30 cm, it is classified as short, while a long umbilical cord is over 80 cm. The length of the cord affects the mobility of the fetus, therefore it is important to examine this feature. Furthermore, the degree of coiling of the umbilical cord should be determined (CI: coiling index) as the absence of coiling

The amniotic fluid is made by the placenta and the membranes before 16–18 weeks, while after 16 weeks, fetal kidneys gradually takes over the production up until birth. Kidneys excrete around 5 ml/h of urine after 20 weeks, which increases to 50 ml/h by the end of pregnancy. Abnormal quantity of the amniotic fluid may indicate a congenital malformation or chromosomal abnormality. Amniotic fluid index (AFI) is an objective method for determining the amount of the amniotic fluid. In the "four quadrant technique," the vertical length of each pocket of fluid is measured in each of the four quadrants and then the measurements are summarized. A normal AFI is 8–24 cm after 16 weeks of gestation. The other technique is the "single deepest pocket" technique measures the vertical length of the deepest pocket with a

Oligohydramnios is the condition when there is less amniotic fluid than the normal (less than

• Grade II: 30–36 weeks, deeper indentations, echodensities

brain and urogenital malformations and Trisomy 13 or 18 [57, 58].

may suggest chromosomal abnormality, fetal distress or retardation [57, 58].

normal value of 2–8 cm. The latter is mostly used in twin pregnancies [57, 58].

ine growth retardation [55, 57, 58].

**11. Amniotic fluid**

500 ml in the third trimester).

Club-foot (**Figure 5**) is the most prevalent congenital malformation of the extremities with a birth prevalence of 1:1000. However, according to some studies, the malformation occurs in 1:250 in utero [54]. The affected foot is rotated internally. In half of the cases, both feet are affected and club-foot is associated with other abnormalities (such as Trisomy 18). Also, it may occur as part of the Potter-sequence, or in neuromuscular anomalies, neural tube defects or amniotic band constriction [54].

**Figure 5.** Club-foot. On the picture the affected foot is rotated internally.

In our study, malformations of the skeleton were diagnosed with a higher sensitivity than anomalies of the extremities (82.93% vs. 37.5%). We found higher ultrasound sensitivity in osteogenesis imperfecta (80%), reduction deformities (64.71%), and club foot (51.43%). Ultrasound was less effective in diagnosing hip dysplasia and malformations of the fingers.
