Fetal Down Syndrome Research Articles

Habituation in normal and Down's syndrome fetuses.

The ability of ten normal and two Down's syndrome fetuses to habituate to a repeated auditory stimulus was assessed. The normal fetuses were assessed on two separate occasions during the final trimester of pregnancy. The number of trials to habituate and latency to respond were recorded. The results demonstrated that all normal fetuses exhibited a decrement in response to repeated presentations of the stimulus, a 250-Hz sine wave. This was the result of habituation and not fatigue since fetuses recovered responding upon presentation of a new (500 Hz) stimulus and habituated faster on re-presentation of the original stimulus. The performance of fetuses remained stable over the two testing periods. The response of the Down's syndrome fetuses was different to that of normal fetuses rarely overlapping indices of habituation exhibited by normal fetuses. The study concludes that habituation may be a powerful tool to examine the behavioural and sensory development of the fetus and may be of use in the antenatal assessment of the existence and severity of neural abnormality.

Can Sonographers Reliably Identify Anatomic Features Associated with Down Syndrome in Fetuses?

Can Sonographers Reliably Identify Anatomic Features Associated with Down Syndrome in Fetuses?

Can sonographers reliably identify anatomic features associated with Down syndrome in fetuses?

To standardize femur measurement for the identification of fetuses at risk for Down syndrome, sonographers of varying professional experience and background measured the femurs of 20 Down syndrome fetuses and 709 normal control fetuses. A regression analysis performed to compare biparietal diameter to femur length on the 709 control fetuses yielded the following formula: expected femur length = -9.3105 + 0.9028.biparietal diameter. A ratio of measured-to-expected femur length of 0.91 or lower indicated Down syndrome with a sensitivity of 40%, a specificity of 95%, and a positive predictive value of 3.1%. Eight of the 20 fetuses with Down syndrome (40%) also had a thickened nuchal fold (6 mm or larger). If the nuchal fold findings had been considered with the femur length findings, two more of the fetuses with Down syndrome would have been identified, yielding a sensitivity of 45% and a positive predictive value of 4.3%. Because these measurements were made by eight sonographers rather than a single experienced sonologist, these results could be achieved in most ultrasound laboratories where measurements are done primarily by sonographers.

Down syndrome: sonographic sign for diagnosis in the second-trimester fetus.

In an expanded series of patients a sonographic sign was found to correlate well with the diagnosis of Down syndrome in second-trimester fetuses. The sign is characterized by soft-tissue thickening at the back of the fetal occiput. Sonographic evaluation for this sign was done in 2,121 consecutive fetuses between 15 and 20 gestational weeks of age at the time of genetic amniocentesis. The mothers were 35 years old or older or were otherwise at increased risk for fetal trisomies. Ten fetuses had Down syndrome by karyotype and four of these (40%) had thickened soft tissues (6 mm or more) at the back of the neck or occiput. When these data are combined with those in series previously reported by the authors, similarly collected consecutively, total second-trimester fetuses studied equals 3,825. Nine of the 21 (42%) Down syndrome fetuses by karyotype from this 3,825 had the positive sonographic sign described.

Maternal serum alpha‐fetoprotein and fetal trisomy‐21 in women 35 years and older: Implications for alpha‐fetoprotein screening programs

A retrospective study of 3,411 women who underwent midtrimester amniocentesis for fetal chromosome analysis between June 1979 and August 1984 was performed to evaluate an association between low maternal serum alpha-fetoprotein (AFP) concentrations and Down syndrome (DS) pregnancies. A total of 71 pregnancies was found with abnormal fetal chromosomes; of these, 26 cases were trisomy-21 and 10 cases were trisomy-18. The maternal serum AFP in women with DS fetuses was relatively lower than levels in women with fetuses that had normal chromosomes. In addition, the AFP concentrations in amniotic fluid were decreased in cases involving DS fetuses. We have estimated the risks for DS pregnancy at all maternal ages and most serum AFP concentrations. Using these calculations, genetic counselors will be able to provide more accurate risk estimates for trisomy-21 following maternal serum AFP testing.