Justifiability of amniocentesis on the basis of positive findings of triple test, ultrasound scan and advanced maternal age

Abstract

Objective. To assess the effectiveness of antenatal screening for chromosomal abnormalities based on maternal age (≥35 years), positive ultrasound findings or a positive triple test. Materials and methods. Retrospective six-year study. The pregnant women routinely underwent established clinical and laboratory practice at the Department of Medical Genetics between 1997 and 2003. The women's case notes were examined to identify indications for karyotyping, gestation period and the outcome of karyotyping and pregnancy. Results. Invasive antenatal tests were performed on 1440 cases, 1168 (81.11%) age 35(a), 72 (5.00%) positive triple test (b), 24 (1.67%) positive ultrasound scanning (c) and 176 (12.2%) other (psychological, personal reasons, etc) (d). The overall positive predictive value was 1.67% (1.6%(a), 1.4% (b), 12.5% (c), 0.0% (d). The constructed model of logistic regression gave an odds-ratio of 8.647 for the "positive ultrasound result vs. maternal age ≥35" indication, while the odds-ratio for the triple test vs. maternal age ≥35 was 0.854. Conclusions. Amniocentesis and cytogenetic analysis of foetal karyotype should be presented as a diagnostic possibility to all women over 35 years. The application of biochemical markers was far from the expected results. If we compare results for indication positive ultrasound scanning vs. maternal age, an oddsratio of ~9 was obtained. These results demonstrate that the likelihood of obtaining positive results (i.e. the presence of chromosome alterations) from an amniocentesis having this indication is almost 9 times higher than from having an amniocentesis performed solely for advanced maternal age.

Analysis of the Results of Amniocentesis Performed at the University Clinical Centre of the Republic of Srpska

“…PPV of indication abnormal screening markers in maternal serum was 1.36%, which was similar to that in studies in region (1.40% and 1.60%), 8,9 but was significantly smaller to that reported in countries with long history of prenatal screening (2.60% and 3.50%). 12,13 Indication family history of chromosomal aberrations or congenital anomalies had very small PPV in prenatal detection of chromosomal aberrations in our study (0.55%).…”

“…PPV of indication advanced maternal age was 2.34% which was similar to that reported in other studies (2.3% -4.5%). 9,10,12,18 This indication had the highest PPV in detection numerical autosomal aberrations (0.90%).…”

“…This result is similar to result in the report of Milošević Đerić et al (63%) and smaller than results of the other studies from region (78% -80%). [8][9][10] In contrast, in countries in which prenatal screening policy is adopted, the proportion of this indication was even smaller (18% and 45%). 9,10 This is due to the fact that most developed countries have national guidelines that recommend fetal aneuploidy screening prior to invasive testing.…”

“…[8][9][10] In contrast, in countries in which prenatal screening policy is adopted, the proportion of this indication was even smaller (18% and 45%). 9,10 This is due to the fact that most developed countries have national guidelines that recommend fetal aneuploidy screening prior to invasive testing. In the Republic of Srpska, however, fetal aneuploidy screening using a screening ultrasound and markers in maternal serum hadn't been routinely offered to pregnant women before 2012.…”

“…A total of 94 chromosomal aberrations were found among 3994 amniotic fluid specimens, so overall abnormality rate was 2.35% which was similar to that reported in previous studies in other countries (1.67% -3%). [7][8][9][10][12][13][14][15][16][17] However, it varied by indication. The highest PPV in detection of chromosomal aberrations had indication parent carrier of chromosomal aberration (35.29%).…”