Accuracy of prenatal diagnosis and prediction of lethality for fetal skeletal dysplasias

Abstract

We report higher prenatal/postnatal concordance rates in this series. A precise prenatal diagnosis is frequently difficult and often inaccurate. Prediction of lethality is much easier and often possible with accuracy. Parents need to be aware that the outcome of many skeletal dysplasias is poor.

Best practice guidelines regarding prenatal evaluation and delivery of patients with skeletal dysplasia

“…A recent series reported that the suspected prenatal diagnosis was correct in only 79.3%. 49 Therefore, we concurred that postnatal skeletal survey is helpful in the diagnosis of skeletal dysplasia as well as molecular testing, if available.…”

“…Early features of some skeletal dysplasias can be detected at this time, such as short limb length (femur length [FL] or humerus length <5th percentile or >2 SD below the mean 48 and angulation and deformity of long bones, although precise prenatal diagnosis is often difficult. 49 Additional sonographic findings such as congenital heart disease, renal and brain anomalies, and other skeletal anomalies can also discriminate between various syndromes and skeletal dysplasias. Less uniformly available is 3dimensional (3D) ultrasound, which can assist in the assessment of facial features that are characteristic of certain disorders.…”

Antenatal diagnosis and management of life-limiting conditions

“…In particular, the finding of a small chest with multiple rib fractures is significantly associated with perinatal lethality. 48 Whereas a specific diagnosis of the dysplasia is not always possible prenatally, 49 advances in molecular genetics now allow a definitive prenatal diagnosis to be made using non-invasive diagnostic techniques in some cases. 43 Although some skeletal dysplasias exhibit considerable genetic heterogeneity, in many cases a specific molecular diagnosis can be made.…”

“…In cases of skeletal dysplasia, a pathologist and radiologist can often make a confident diagnosis using non-invasive plain radiography alone. 48,51 Cytogenetic testing requires further samples, either from the placenta, or fetal/neonatal blood or skin samples to confirm a prenatal diagnosis of a chromosomal abnormality.…”

Evaluation of the Child with Short Stature

“…18,19 It should be remembered that as many as 80% of prenatally detected skeletal dysplasias are lethal, and thus the prenatal cohort and the live birth cohort are epidemiologically distinct. 20 Understanding this allows one to properly interpret the differential prevalence between live births and still births (3.0 per 10,000 vs 20.0 per 10,000). 21 A powerful rule of thumb is that until proven otherwise, age-adjusted fetal femoral length of less than 40% indicates achondrogenesis, 40% to 60% is consistent with osteogenesis imperfecta type II or thanotophoric dysplasia, and greater than 80% of femoral length points to osteogenesis imperfecta type III or achondroplasia.…”