First trimester screening driven diagnostic procedures and outcomes: 4 year experience

Objective

In this study we aimed to present the distribution of the risk results detected by routine first trimester combined screening and screening driven procedures together with the demographic and clinical properties of the patients.

Methods

Data of the routine first trimester combined screening of singleton pregnancies performed between 2008 and 2011 were evaluated in this cross-sectional and retrospective study. Patients had test after NT measurements within the same day. Screening driven procedures like cordocentesis and amniocentesis were re-evaluated for their indications, frequencies and karyotype results. Patient groups of cordocentesis and amniocentesis were compared for perinatal prognosis.

Results

A total of 1109 patients were included for data analyses. Mean maternal age of screened pregnant women was 31.07±3.73 years. Mean values of related biochemical parameters were as: fBhCG: 1.26±0.94 MoM and PAPP-A 1.16±0.65 MoM. When a cut off value of 1/250 is chosen for combined test detected risk, screening was positive in 3,15% of the patients (35/1109). In addition, 22 cases were performed invasive procedures irrespective of combined test and when second tirmster screening was taken into account 19 more patients were performed invasive procedures (A total of 6,4%). In 7.4% of the patients, abnormality was present in the karyotype analysis. These were; Trisomy 21 (n=3), Trisomy 18 (n=2), mosaic XXY (n=2), inversion -inv9(p11q12)- (n=1) and triploidy (n=1). Abnormality in the karyotype analysis was more frequent in the patinets with positive first trimester combined screening compared to patients performed invasive procedures solely for maternal age, anxiety, second trimester screening or positive sonographic screening alone. Invasive procedures resulted an outcome of rate of approximately 13% chromosomal abnormality and pregnancy termination in approximately 10%. No abnormality necessitating pregnancy termination was encountered in invasive procedures performed due to anxiety of doctor or mother.

Conclusions

Though false positive rate of routine first trimester combined screening test is 3,1% in our study, total rate of invasive procedures exceeds the double of this rate (6,4%). An old habit of the anxiety related to maternal age increases rate of invasive procedures. When procedures performed with indications of NT alone or biochemical test alone, are taken into account this rate further increases.

Keywords

First trimester screening, amnicentesis, cordocentesis

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