echogenic cardiac focus, relatively short femur and short humerus, iliac wing angle, on the scan, and individualized genetic counseling would be recommended. and does not bear any relationship with heart abnormalities of the baby. Request PDF on ResearchGate | Humerus and femur length in fetuses with Down syndrome | The The median femur and humeral lengths in DS fetuses were times the expected values. These data are useful for counseling women who are at increased Down syndrome risk and To determine the relationship. To assess the relationship between the finding of fetal femur diaphysis .. This has to be taken into account when counseling the parents about.
Skeleton - DIAGNOSIS OF FETAL ABNORMALITIES - THE WEEKS SCAN
The following fetal ultrasound parameters must be visualized and plotted against normative values when a fetus manifesting a skeletal dysplasia is suspected Table 1 ; fetal cranium biparietal diameter, occipital-frontal diameter, and head circumferenceabdominal circumference, mandible, clavicle, scapula, chest circumference, and all fetal long bones.
Comparison of the relative length of all the long bones and against normative values will determine whether there is primarily rhizomelia, mesomelia, or that both segments are involved. One helpful ratio is the femur to foot ratio, which approaches 1.
Many skeletal dysplasias show disproportion based on those parameters. In addition to evaluation of the long bones, there are other ultrasound parameters that should be evaluated and can be helpful in these differentiating disorders Table 1. These include the fetal facial profile glabellar bossing, flattened nasal bridge, micrognathia; Fig. There are many prenatal onset skeletal dysplasias that are associated with relative brachydactyly and equinovarus Table 2. Fetuses with long bone measurements more than 3D below the mean should be strongly suspected of having a skeletal dysplasia, especially if the head circumference is greater than the 75th centile.
Most prenatal-onset skeletal dysplasias present with relative disproportion of the skeletal measurements when compared with those of the cranium. In addition, close attention should be paid to the shape and mineralization pattern of the fetal calvarium and fetal skeleton poor or ectopic mineralization. Determining the elements of the skeleton that are abnormal, coupled with the findings of mineralization and shape of the bones can aid in diagnosis Table 2.
Appropriate consultation with a geneticist or genetic counselor is recommended to assess the constellation of abnormalities and determine the most likely differential diagnoses. Prognosis and natural history can then be discussed using the most likely diagnoses as the basis for discussion. Some disorders are referred to by eponyms such as Ellis—Van Creveld syndromeby Greek terms describing a salient feature of the disease diastrophic or twisted, metatrophic or changeable or by a term related to the presumed pathogenesis of the disease such as osteogenesis imperfecta.
The fundamental problem with any classification of skeletal dysplasias is that the pathogenesis of these diseases is largely unknown and, therefore, the current system relies on purely descriptive findings of either clinical or radiological nature.
According to the International Nomenclature for Skeletal Dysplasias, the diseases are subdivided into three different groups: Approach to prenatal diagnosis There is a wide range of rare skeletal dyplasias, each with a specific recurrence risk, dysmorphic expression, and implications for neonatal survival and quality of life. Our knowledge of the in utero expression of these syndromes is based on a few case reports and, therefore, in attempting to perform prenatal diagnosis of individual conditions in at-risk families, extrapolation of findings from the perinatal period is often necessary.
The incidental discovery of a skeletal dysplasia on routine ultrasound screening, in a pregnancy not known to be at risk of a specific syndrome, necessitates a systematic examination to arrive at the correct diagnosis. All limbs must be evaluated see Figure 17, p. Assessment of long bones Shortening of the extremities can involve the entire limb micromelia, such as achondrogenesis, short-rib polydactyly syndrome, diastrophic dysplasia osteogenesis imperfecta type IIthe proximal segment rhizomelia, such as achondroplasiathe intermediate segment mesomelia, such as mesomelic dysplasia or the distal segment acromelia, such as Ellis—Van Creveld syndrome.
The diagnosis of rhizomelia or mesomelia requires comparison of the dimensions of the bones of the leg and forearm with those of the thigh and arm. The femur, however, is abnormally short even in mesomelic dwarfism and, therefore, in our routine fetal abnormality screening, we tend to confine limb measurements to that of the femur.
When dealing with pregnancies at risk for a skeletal dysplasia, both segments of all limbs are measured.
Guidelines for the prenatal diagnosis of fetal skeletal dysplasias
The severe limb reductions associated with osteogenesis imperfecta type II, achondrogenesis and thanatophoric, diastrophic, and chondroectodermal dysplasias can be detected by a single measurement of the femur length at 16—18 weeks of gestation.
In the case of achondroplasia, however, the diagnosis may not become obvious until 22—24 weeks and, therefore, serial measurements are necessary; homozygous achondroplasia, which is usually lethal, manifests in abnormally short limbs earlier than the heterozygous form.
- Guidelines for the prenatal diagnosis of fetal skeletal dysplasias
A minor degree of lateral curvature of the femur is commonly seen in normal fetuses. Pronounced bowing, however, is observed in association with campomelic dysplasia, thanatophoric dwarfism, autosomal dominant osteogenesis imperfecta, achondrogenesis and hypophosphatasia.
In the latter, fractures and callus formation may also be detected.
Outcome of Fetuses with Diagnosis of Isolated Short Femur in the Second Half of Pregnancy
Reduced echogenicity of bones, suggestive of hypomineralization, is seen in such disorders as hypophosphatasia, osteogenesis imperfecta and achondrogenesis. The virtual absence of ossification of the spine, characteristic of achondrogenesis, may lead to the erroneous diagnosis of complete spinal agenesis.
Similarly, the pronounced clarity with which the cerebral ventricles are imaged, as a result of the poorly mineralized globular cranium in cases of hypophosphatasia, may result in the misdiagnosis of hydrocephalus. Care must be exercised, however, because lesser degrees of hypomineralization may not be detectable. Isolated limb reduction deformities, such as amelia complete absence of extremitiesacheiria absence of the handphocomelia seal limb or aplasia—hypoplasia of the radius or ulna, are often inherited as part of a genetic syndrome Holt—Oram syndrome, Fanconi pancytopenia, thrombocytopenia with absent radii syndrome and are readily diagnosible by ultrasonography in an at-risk fetus.
Other causes of focal limb loss include the amniotic band syndrome, thalidomide exposure and caudal regression syndrome. Evaluation of hands and feet Fetal fingers and toes can be seen, and, with meticulous examination, abnormalities of numbers, shape, movement and attitudes can be recognized.Making Marriage Work - Dr. John Gottman
Several skeletal dysplasias feature alterations of the hands and feet. Polydactyly refers to the presence of more than five digits. It is classified as postaxial if the extra digits are on the ulnar or fibular side and preaxial if they are located on the radial or tibial side. Syndactyly refers to soft tissue or bony fusion of adjacent digits. Clinodactyly consists of deviation of a finger s. Disproportion between hands and feet and the other parts of the extremity may also be a sign of a skeletal dysplasia.
Examination of fetal movements Maternal perception of fetal movements is usually decreased in fetuses with skeletal dysplasias, such as achondrogenesis and thanatophoric dysplasia. Ultrasonography can aid in the diagnosis of conditions characterized by limitation of flexion or extension of the limbs, such as arthrogryposis and multiple pterygium syndrome.
Evaluation of thoracic dimensions Several skeletal dysplasias are associated with a small thorax, and chest restriction leads to pulmonary hypoplasia, which is the common cause of death in these conditions.