Research

Wealthier pregnant women more likely to have noninvasive screening

Pregnant women in the wealthier suburbs of Victoria are five times more likely to have used a state-of-the-art Down syndrome screening test before an invasive procedure, compared with women from socioeconomically-disadvantaged regions.

Results from a study of women having prenatal diagnosis in Victoria during 2014-15 have shown that women from socioeconomically disadvantaged areas were less likely to use non-invasive prenatal testing (NIPT) and more likely to rely on older and less accurate screening tests to make their decisions regarding invasive testing during pregnancy.

All pregnant women in Australia are offered voluntary screening in the form of a blood test +/- ultrasound to assess the chance of their fetus having a chromosome condition such as Down Syndrome. If the screening test shows an increased chance of a chromosome condition, a woman is offered genetic counselling and the option of confirmatory invasive testing with amniocentesis or chorionic villus sampling for a definitive diagnosis.

The two traditional prenatal screening tests – combined first trimester screening and second trimester serum screening – can erroneously identify 4-7% of normal pregnancies as having an increased chance of a chromosome abnormality. These so-called ‘false positive’ results lead to a substantial number of women with normal fetuses undergoing invasive prenatal diagnosis for confirmation.

NIPT, a DNA sequencing-based method that analyses cell-free fetal DNA in maternal blood, became widely available in Australia in 2013 and is well recognised as the most effective screening tool for Down syndrome. NIPT is much more accurate than traditional screening tests and its uptake by Australian women has reduced the overall numbers of unnecessary invasive prenatal tests dramatically. However, the substantial cost of NIPT (around $500, with no Medicare or private health insurance rebate), has raised significant ethical concerns regarding its access to financially disadvantaged women.

These concerns led A/Professor Lisa Hui from the Murdoch Children’s Research Institute to analyse state-wide data on women undergoing amniocentesis or chorionic villus sampling from Jan 2014 to Dec 2015. Women were included in the analysis if their primary reason for having invasive prenatal diagnosis was their result from combined first trimester screening, second trimester serum screening or NIPT. Postcodes were used to allocate socioeconomic status based on Australian Bureau of Statistics Census data.

This study’s state-wide dataset provides the first quantitative evidence that the benefits of NIPT appear to be skewed towards women living in the most socioeconomically advantaged areas, supporting concerns about the inequitable access to NIPT and other genomic advances.

The consequences of this disparity is that women from disadvantaged regions are more likely to undergo unnecessary invasive testing as a result of false positive screening results. About 1 in 3 women from the most advantaged areas had a fetal chromosome condition diagnosed after confirmatory diagnostic testing, compared with only 1 in 7 women from disadvantaged areas. As invasive testing carries a small risk of miscarriage, this suggests that women from socioeconomically-disadvantaged areas may be unnecessarily exposed to this risk more frequently than advantaged women.

Source: Royal Australian and New Zealand College of Obstetricians and Gynaecologists

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