| Objective:In recent years,a new method of prenatal screening has emerged:Prenatal screening of fetal free DNA from maternal peripheral blood.Fetal cell-free DNA(cff DNA)fragments were found in maternal peripheral blood,and these fragments were enriched for detection and analysis in order to screen for fetal aneuploidy,prenatal screening of fetal free DNA in maternal peripheral blood.This is a Non-invasive test,also known as Non-invasive Prenatal testing,or NIPT.In this study,the sensitivity,specificity,positive predictive value,negative predictive value and other indicators of NIPT for prenatal screening of fetal chromosomal aneuploidy abnormalities in elderly pregnant women were analyzed to evaluate the difference between prenatal screening and direct invasive prenatal diagnosis of fetal chromosomal aneuploidy in elderly pregnant women.At the same time,according to the different age of the expected date of confinement(EDC)of the elderly pregnant women included in the study,it was compared in sections to compare the occurrence of fetal chromosome aneuploidy in different age groups,and on this basis,an optimized prenatal screening and prenatal diagnosis program for elderly pregnant women was proposed.Methods:11,271 pregnant women,including pregnant women of advanced age and serological screening for high risk pregnancy,were selected for the study from January 2016 to December 2018 at Jinan Maternal and child health care hospital,NIPT or amniotic fluid prenatal diagnosis was selected according to informed consent and divided into four groups:Group A was aged pregnant women who chose Nipt with informed consent;Group B was pregnant women who chose NIPT with informed consent for serological prenatal screening;Group C was pregnant women who chose Nipt with informed consent;Group D was serological prenatal screening with high risk of direct amniotic fluid prenatal diagnosis.They were followed up for the outcome of pregnancy.Among them,the prenatal diagnosis of amniotic fluid was based on the results of fetal karyotype analysis,while the NIPT test was performed in low-risk pregnant women,who were followed up and evaluated by neonatal outcomes.SPSS(version 22.0)software was used for statistical analysis of the data to analyze the efficiency of the application of NIPT in pregnant women of different ages and the incidence of fetal chromosome aneuploidy abnormalities in elderly pregnant women of different ages.Result:①The age at delivery of the elderly pregnant women included in the study ranged from 35 to 50 years old,with an average age of 39.48±3.83 years.The mean gestational weeks of NIPT were 16.18±1.05 weeks,ranging from 12 to 30 weeks.② A total of 5050 cases were included in the study,107 of them were NIPT positive,the positive rate was 2.11%.Among them,89 pregnant women underwent invasive prenatal diagnosis.The results showed that there were 29 cases of T21,13 cases of T18,2 cases of T13,6 cases of sex chromosome abnormalities,and 7 cases of other chromosome abnormalities.Thirteen of the 18 cases without prenatal diagnosis of amniotic fluid terminated pregnancy,but none of them were detected by fetal genechip.Two cases were lost.The other 3 cases were all delivered,and no obvious abnormality was observed by telephone follow-up.③The positive rate of NIPT was 0.98%(16/1631)in Group B,and 15 of them chose invasive prenatal diagnosis again.The results showed that there were 4 cases of T21,0 case of T18,1 case of T13,2 cases of abnormal sex chromosome and 1 case of T20.The results of other pregnant women were normal.Another pregnant woman with abnormal number of sex chromosomes was detected by NIPT.During the second trimester of pregnancy,the fetus died in uterus and the chromosomes of induced fetus were not examined.④In group C,1401 pregnant women with invasive prenatal diagnosis were included in the study.The positive rate was 2.36%.Among them,there were 17 cases of T21,7 cases of T18,0 cases of T13,3 cases of sexual chromosome abnormalities and 6 cases of other chromosome abnormalities.The results of other chromosome polymorphisms were not included in the positive results.⑤In group D,3189 pregnant women were included in the study.41 pregnant women were diagnosed as chromosomal aneuploidy positive by prenatal examination,and the positive rate was about 1.29%.Among them,25 were trisomy 21,trisomy 18 and trisomy 13.The other 16 pregnant women were detected as sex chromosome abnormalities,chromosomal chimeras,microdeletion or microduplication syndrome.⑥There was no significant difference in the detection rate of fetal aneuploidy between Group A and Group C(P>0.05),and the detection rate of fetal aneuploidy was similar between Group B and Group D(P>0.05).⑦ The coincidence rate of NIPT in the diagnosis of different chromosomal abnormalities was also significantly different when it was used for screening of fetal chromosomal aneuploidy genes.Among them,the coincidence rate of 21-trisomy was the highest,reaching 94.29%,while that of other chromosomal abnormalities was the lowest,only 19.51%.⑧According to the different ages of pregnant women in A and C groups,the difference of results was analyzed.It can be seen that the occurrence of fetal aneuploidy chromosomal diseases in different ages is also different.According to this difference,we put forward the optimization scheme of prenatal screening for the older pregnant women.Conclusion:The technique of cell-free fetal DNA in maternal plasma for noninvasive prenatal screening is effective in the detection of elderly pregnant women,and suitable for screening of fetal aneuploidy of elderly pregnant women.For pregnant women under the age of 41 years old who have not been combined with the other clear evidence of interventional prenatal diagnosis,NIPT can be used as the first choice for fetal common chromosome aneuploidy screening,prenatal diagnosis was performed based on NIPT findings,as appropriate,to reduce the incidence of surgical complications.For pregnant women over 41 years of age,we still suggest that they should choose the interventional prenatal diagnosis directly to reduce the possibility of missed screening. |
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