Women at increased risk for trisomy 21 who have suffered previous miscarriages and have a lower level of education are those most likely to refuse amniocentesis during pregnancy, a group of Polish researchers reported in BMC Pregnancy and Childbirth.
Amniocentesis is the most commonly performed prenatal invasive diagnostic test in the second trimester, and can accurately predict risk of Down syndrome through detection of trisomy 21. It is therefore curious that some pregnant women with a heightened fetal risk for chromosomal abnormalities refuse amniocentesis. To investigate the reasons behind their reluctance, the group analyzed data for 177 women carrying singleton pregnancies who had a personalized risk score for trisomy 21 >1:300, which the Polish Gynecological Society deems a heightened risk for fetal chromosomal aberration. The personalized risk score was calculated in the study on the basis of measurement of nuchal translucency (NT) on ultrasound and blood levels of free-b-human chorionic gonadotrophin (b-hCG) and pregnancy-associated plasma protein-A (PAPP-A) between 11 and 14 weeks of pregnancy. When paired with maternal age, this score has been shown to have a sensitivity of 85% to 95% in detecting trisomy 21 with a 5% false-positive rate.
One hundred twenty-five patients underwent amniocentesis and 52 refused the test. A statistically significant relationship was found between refusal and women who had suffered at least two miscarriages during previous pregnancies compared to women who had not. Maternal educational levels were also significantly associated with refusal, and women with only a primary education were more likely to decline amniocentesis than women with higher levels of education. Both primary maternal education and a history of at least two miscarriages were found to be independent, significant predictors of refusal of amniocentesis. An NT< 2.5 mm at 11 to 14 weeks’ gestation was another factor for declining the diagnostic procedure. Women with lower personalized risk scores for trisomy 21 were less likely than women with higher scores to opt for amniocentesis. Refusal did not correlate significantly with maternal age, number of pregnancies, marital status, or gestational age.
Education about amniocentesis risks and benefits
Previous studies indicate that many pregnant women lack understanding of their options for prenatal screening, and the nature, risks, and benefits of the examinations and tests. This is true even of well-educated and economically stable individuals, reported the authors. Thus, parents are not able to make an informed choice about amniocentesis, which must be accomplished within a tight timeframe during pregnancy to be performed safely and yield accurate findings.
Most pregnant women also do not consider the risk of potential problems with their babies, and most do not discuss the risks with their partner or another person when referred for fetal health assessment. The investigators suggested that, coupled with heightened levels of anxiety and stress, they may be in a high level of denial or not prepared for a diagnosis of trisomy 21.
Pregnant women need to be educated about the important role of high-quality, accurate, non-invasive diagnostic tests such as NT and blood tests to screen for fetal chromosomal anomalies and the risks and benefits of amniocentesis, according to these authors. Many women fear that amniocentesis may induce miscarriage. Estimates suggest the risk is low, however, varying from 1:100 to 1:1,600.
Women who decide against amniocentesis may be offered noninvasive prenatal testing (NIPT) such as measurement of cell-free DNA in maternal plasma, which can identify trisomy 21 pregnancies beginning at 10 weeks with high accuracy (> 99%) and a low false-positive rate (0.1%). Results of NIPT, however, need to be confirmed by amniocentesis.