Abstract
Background: We aimed to assess the clinical application of noninvasive prenatal screening (NIPS) based on second-trimester ultrasonographic soft markers (USMs) in low-risk pregnant women. Methods: Data of pregnant women between April 2015 and December 2019 were retrospectively analyzed. Pregnant women [age at expected date of confinement (EDC) of <35 years; low risks for trisomy 21 (T21) and trisomy 18 (T18) based on maternal serum screening; presenting second-trimester USMs (7 types)] who successfully underwent NIPS and had available follow-up information were included in our study. Cases with positive NIPS results were prenatally diagnosed. All patients were followed up for 6 months to 2 years after NIPS, and their clinical outcomes were obtained. Subgroup analyses were performed according to the different USMs. Results: NIPS suggested that among a total of 10,023 cases, 37 (0.37%) were at high risk of aneuploidy, including 4 T21, 6 trisomy 13 (T13), and 27 sex chromosome abnormalities (SCA). Ten cases with aneuploidy (0.10%) were confirmed by prenatal diagnosis, consisting of two T21 and eight SCA. The eight fetuses with SCA consisted of one monosomy X, two XXY, one XXXY, one XXX, one XYY, and two mosaicisms. T21 was detected in one fetus with absent or hypoplastic nasal bone and one fetus with echogenic intracardiac focus (EICF). SCA was detected in five fetuses with EICF, two fetuses with multiple soft markers, and one fetus with echogenic bowel. The positive rate of chromosomal aneuploidy was significantly higher in fetuses with absent or hypoplastic nasal bone (6.25 vs. 0.10%, p = 0.017), echogenic bowel (3.7 vs. 0.10%, p = 0.029), and multiple soft markers (0.678 vs. 0.10%, p = 0.045) than in the total fetuses. The positive predictive values (PPVs) of NIPS in these three groups were 100%, 50%, and 100%, respectively. EICF accounted for 93.25% (9,346/10,023) of the study population, whereas the PPV of NIPS was only 20%. Conclusion: NIPS is an advanced screening test for low-risk pregnant women. In the 10,023 pregnant women sampled, SCA were more common than autosomal trisomy, and EICF was the most frequent USM but the least predictive aneuploidy. Further aneuploidy evaluation is suggested for low-risk pregnant women whose ultrasound indicates absent or hypoplastic nasal bone, echogenic bowel, or multiple soft markers. NIPS can serve as a second-line complementary screening for these women.
Highlights
With the rapid development of ultrasound technology for application in the first and second trimesters, an increasing number of small ultrasound markers have been discovered, that is, ultrasonographic soft markers (USMs)
The inclusion criteria were as follows: (1) age at the expected date of confinement (EDC) of less than 35 years; (2) low risk for trisomy 21 (T21) and trisomy 18 (T18) based on maternal serum screening; (3) indication of USMs according to second-trimester ultrasound; and (4) noninvasive prenatal screening (NIPS) case
The sensitivity, specificity, positive predictive value (PPV), and negative predictive value of NIPS, respectively, were as follows: for T21: 100%, 99.98%, 50.00%, 100%; for SCA: 100%, 99.81%, 29.63%, and 100%
Summary
With the rapid development of ultrasound technology for application in the first and second trimesters, an increasing number of small ultrasound markers have been discovered, that is, ultrasonographic soft markers (USMs). USMs are closely associated with fetal chromosomal abnormalities and adverse pregnancy outcomes. The association between nuchal translucency thickness and Down syndrome was first reported in the 1980s (Benacerraf et al, 1985). Diverse ultrasound anomalies have been reported to be associated with trisomy 21 (T21) (Nyberg and Souter, 2001), such as echogenic intracardiac focus (EICF), absent or hypoplastic nasal bone, and mild pyelectasis. Several studies have shown that USMs increase the incidence of invasive prenatal puncture surgery (Ahman et al, 2014). We aimed to assess the clinical application of noninvasive prenatal screening (NIPS) based on second-trimester ultrasonographic soft markers (USMs) in low-risk pregnant women
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