Objective To explore the value of non-invasive prenatal test (NIPT) in pregnant women with intermediate risk after traditional Down syndrome screening. Methods From March 1 2015 to March 31 2016, a total of 2 949 pregnant women with intermediate risk after traditional Down syndrome screening who received NIPT as the second-line screening method at Shenzhen Maternity and Child Healthcare Hospital after informed consent were recruited for this study. Retrospective data analysis including the results of traditional Down syndrome screening, ultrasound, NIPT and invasive amniocentesis to fetal karyotype analysis were conducted, and pregnant outcomes were followed up. Results NIPT results were all obtained in 2 949 pregnant women with intermediate risk after traditional Down syndrome screening. Of 25 NIPT-positive cases, 24 cases received invasive amniocentesis to fetal karyotype analysis. Thirteen cases were confirmed with fetal chromosomal abnormalities including 5 cases of trisomy 21, 2 cases of trisomy 13, 4 cases of sex chromosomal abnormalities and 2 cases of other chromosomal abnormalities. In addition, 1 NIPT-positive case refused prenatal diagnosis was confirmed normal result after birth. The postnatal follow-up in NIPT-negative women did not find any newborn with chromosomal abnormality. The incidence of fetal chromosomal abnormalities in women with intermediate risk was 0.44% (13/2 949). Conclusion NIPT can be used as second-line screening method in pregnant women with intermediate risk after Down syndrome screening, which could lead to the prenatal detection of a higher proportion of fetal chromosomal abnormalities and a lower invasive-testing rate.

Objective To explore the correlations between measurements of Doppler velocity waveform parameters of fetal main pulmonary artery and gestation age (GA) in normal fetus. Methods This is a cross-sectional study, in which totally 252 normal singleton fetuses between 23 and 40 weeks of gestation were divided into 10 groups. The following velocity waveform parameters were measured in the main trunk of fetal pulmonary artery by Doppler ultrasound: acceleration time(AT), ejection time(ET), acceleration time/ejection time(AT/ET), peak systolic velocity(PSV), end diastolic velocity(EDV), mean velocity(MV), pulsatility index(PI) and resistance index(RI). The normal reference values of Doppler velocity waveform parameters at various GA were established. A scatter diagram of each parameter against GA was plotted out. The optimal formula was selected out according to the correlation and regression analysis. Results Among 252 normal fetuses, satisfactory Doppler velocity waveform of fetal main pulmonary were achieved in 249 (98.8%, 249/252). Among these parameters, AT, AT/ET, PSV, EDV and MV increased with increasing GA(F=343.23, 96.012, 8.649, 2.158, 10.169, all P<0.05), while PI decreased slightly(F=2.346, P<0.05) and ET, RI had no signiifcant changing(F=0.883, 1.534, both P>0.05). Signiifcant and positive linear correlations were found between parameters of AT, AT/ET, PSV, EDV, MV and GA(r= 0.898, 0.868, 0.446, 0.203, 0.507, all P<0.01);while PI was inversely linear correlated with GA(r=-0.184, P<0.01) and ET, RI had no correlation with GA(r=-0.103, 0.011, both P>0.05). Conclusions The fetal main pulmonary artery could be a reliable sampling point to obtain pulmonary velocity waveform by Doppler ultrasound. Doppler velocity waveform parameters have correlations with GA in normal fetus;among which AT and AT/ET were the best.