Evaluation of the usefulness of the fetal femur length with respect to gestational age to detect Down syndrome in Korean subjects

Clinical significance of soft markers in second trimesterr ultrasonography for pregnant Korean women: a multicenter study and literature review

Objective

To evaluate the clinical significance of soft markers for aneuploidy screening in Korean women.

Methods

We retrospectively reviewed the medical records of 5,428 singleton pregnant women who underwent sonography during the second trimester at seven institutions in South Korea. We evaluated the prevalence of the following soft markers: intracardiac echogenic focus, choroid plexus cysts, pyelectasis, echogenic bowel, and mild ventriculomegaly. We developed best-fitted regression equations for the fetal femur and humerus length using our data and defined a short femur and humerus as both long bones below the fifth centile. The results of genetic testing and postnatal outcomes were investigated in patients who had been diagnosed with aforementioned soft markers.

Results

The median maternal age of our study population was 33 years, and the median gestational age at the time of ultrasonographic examination was 21 weeks. We detected soft markers in 10.0% (n=540) of fetuses: 9.3% (n=504) were isolated cases and 0.7% (n=36) of cases had two or more markers. We identified only two aneuploides (trisomy 18, 46,XX,t[8;10][q22.1;p13]), of which one was clinically significant. We presented the neonatal outcomes of the fetuses with the respective soft markers. Preterm delivery, low birth weight, and small-for-gestational-age (SGA) were significantly more common in women with a shortened fetal femur (P<0.001, all). However, the presence of a shortened fetal humerus was not associated with those outcomes excluding SGA.

Conclusion

Soft markers in second-trimester ultrasonography have limited use in screening for fetal aneuploidy in Korean women. However, these markers can be used as a screening tool for adverse outcomes other than chromosomal abnormality.

Influence of second-trimester ultrasound markers for Down syndrome in pregnant women of advanced maternal age

The objective of the present study was to evaluate the influence of second-trimester ultrasound markers on the incidence of Down syndrome among pregnant women of advanced maternal age. This was a retrospective cohort study on 889 singleton pregnancies between the 14th and 30th weeks, with maternal age ≥ 35 years, which would undergo genetic amniocentesis. The second-trimester ultrasound assessed the following markers: increased nuchal fold thickness, cardiac hyperechogenic focus, mild ventriculomegaly, choroid plexus cysts, uni- or bilateral renal pyelectasis, intestinal hyperechogenicity, single umbilical artery, short femur and humerus length, hand/foot alterations, structural fetal malformation, and congenital heart disease. To investigate differences between the groups with and without markers, nonparametric tests consisting of the chi-square test or Fisher's exact test were used. Moreover, odds ratios with their respective 95% confidence intervals were calculated. Out of the 889 pregnant women, 131 (17.3%) presented markers and 758 (82.7%) did not present markers on the second-trimester ultrasound. Increased nuchal fold (P < 0.001) and structural malformation (P < 0.001) were the markers most associated with Down syndrome. The presence of one marker increased the relative risk 10.5-fold, while the presence of two or more markers increased the risk 13.5-fold. The presence of markers on the second-trimester ultrasound, especially thickened nuchal fold and structural malformation, increased the risk of Down syndrome among pregnant women with advanced maternal age.