Anencephaly in a fetus with osteogenesis imperfecta: early diagnosis by transvaginal sonography

Prenatal diagnosis and management of intrauterine fracture

Intrauterine fracture is an extremely rare finding, but can occur as the result of maternal trauma, osteogenesis imperfecta (OI), or theoretically other metabolic/structural abnormalities. Increased clinical awareness of the diagnosis and optimal management of these cases can lead to more positive outcomes for the patient and her child. Blunt abdominal trauma late in gestation increases the risk of fetal skull fracture, while a known diagnosis of OI or other abnormalities leading to decreased fetal bone density creates concern for long bone fracture. Biochemical and genetic tests can aid in the prenatal diagnosis of OI, while ultrasound is the best overall imaging modality for identifying fetal fracture of any etiology. When fetal fracture is diagnosed radiologically, specific management is recommended to promote optimal outcomes for mother and fetus, with special consideration given to the mother with OI. With the exception of fetal fractures due to lethal conditions, cesarean delivery is recommended in most cases, especially when fetal or maternal well-being cannot be assured. When a patient presents with risk factors for intrauterine fracture, careful evaluation via thorough history-taking, ultrasonography of the entire fetal skeleton, and laboratory tests should be performed. Heightened awareness of intrauterine fracture allows better postpartum management, whether for simple fracture care or for long-term care of patients with OI or genetic/metabolic abnormalities.

TARGET AUDIENCE

Obstetricians & Gynecologist, Family Physicians.

LEARNING OBJECTIVES

After completion of this educational activity, the reader will be able to compare x-ray, ultrasound modalities and MRI and their utility in diagnosing fetal fracture. Formulate a differential diagnosis for fetal fracture. Propose a delivery plan for a patient whose fetus has a prenatally diagnosed fetal fracture.

First-trimester diagnosis of osteogenesis imperfecta associated with encephalocele by conventional and three-dimensional ultrasound

To illustrate the three-dimensional sonographic features of a rare genetic disorder, we report on prenatal diagnosis of osteogenesis imperfecta congenita associated with encephalocele at 13 weeks of gestation, using conventional and three-dimensional ultrasound. Because the parents were first-degree cousins and on the basis of the family history, a recessive autosomal inheritance was suspected. Of seven previous pregnancies, five were unaffected and two had been terminated in the second trimester owing to a similar abnormality (one affected boy and one affected girl). In the case we present, the diagnosis was made on the basis of two-dimensional ultrasound performed by physicians aware of the history; the quality of three-dimensional ultrasound imaging suggests that this technique might have contributed toward establishing a precise diagnosis in the absence of a positive family history. Besides, the global view provided by three-dimensional surface-rendering images made the parents more confident of the accuracy of the diagnosis. Although osteogenesis imperfecta congenita is generally considered as autosomal dominant, the case we report suggests that it may be inherited in a recessive autosomal fashion at least when associated with encephalocele. Three-dimensional ultrasound confirmed the conventional two-dimensional examination and was helpful in convincing the parents of the accuracy of the diagnosis.

Reference values for fetal limb biometry at 10-14 weeks of gestation

OBJECTIVES

To calculate reference ranges for fetal limb measurements obtained by transabdominal ultrasound at 10-14 weeks of gestation.

METHODS

Six hundred and six normal fetuses were examined transabdominally in a cross-sectional study by a single observer. The crown-rump length of the fetuses ranged from 31 to 78 mm. Measurement of the length of the humerus, ulna, femur, tibia and foot was attempted from the longest section of each structure. To assess intraobserver repeatability, three sets of repeated measurements were obtained in 26 fetuses.

RESULTS

An appropriate ultrasound measurement was obtained in a percentage of cases ranging from 93.2% to 97.9%. A significant correlation was found between crown-rump length measurements and humerus length (r = 0.74, P < 0.001), ulna length (r = 0.70, P < 0.001), femur length (r = 0.77, P < 0.001), tibia length (r = 0.69, P < 0.001) and foot length (r = 0.58, P < 0.001). Crown-rump length-specific reference ranges for each measurement were calculated with the method of scaled absolute residuals. The study of intraobserver variability showed coefficients of variation ranging from 7.9 to 10.0% and intraclass correlation coefficients ranging from 0.89 to 0.94.

CONCLUSIONS

Fetal limb size is strongly correlated with crown-rump length. Despite a significant biological variability of the measurements, the availability of reference ranges could be of help in the early diagnosis of fetal skeletal dysplasias.

First trimester malformation screening

First trimester fetal malformation screening still represents a diagnostic challenge in modem obstetrics. Being solely dependent on ultrasound instrumentation, and the skill and experience of the operator, recently improved by introducing high frequency transvaginal approach and digital image processing. This opens a new field of ultrasound in obstetrics called sonoembriology. Until now sonoembriology in routine clinical practice resulted in numerous reports about early detection of rare anomalies and uncommon syndromes. The reported sensitivity of sonoembriology with a respect to a final pregnancy outcome was more than 60% of all malformations in total, while in combination with ultrasound screening in second trimester, increases to in excess of 80%. The commonest anomalies detected by sonoembriology are anomalies of the head and brain, heart, abdominal wall, unbilical cord, urinary tract and skeleton. There is an important role of sonoembriology in the assessment of the nuchal translucency in the screening programme for chromosomal anomalies. This changes the well-known concept "fetus as a patient" to "embryo as a patient" and opens new frontiers in fetal diagnosis and therapy.