What is a significant risk factor for false-positive results in any prenatal screening test?

Maternal obesity is particularly significant as a risk factor for false-positive results in prenatal screening tests. This is primarily due to the way that screening tests analyze biomarkers in the blood, which can be influenced by maternal body composition. In cases of maternal obesity, the levels of certain substances that are assessed in screening tests may not correspond accurately with fetal risks, leading to an increased likelihood of obtaining false-positive results.

Moreover, increased body mass may alter the hormonal and biochemical milieu, further complicating the interpretation of test results. Therefore, when maternal obesity is present, it can impact the efficiency and accuracy of screening tests, ultimately affecting clinical decision-making and follow-up.

In contrast, correct dating of the pregnancy, high fetal fraction, and a prior healthy pregnancy are less directly associated with false positives in screening tests. Accurate dating ensures that the gestational age aligns with the expected results of screening tests, while high fetal fraction typically improves test sensitivity and specificity. A prior healthy pregnancy does not inherently increase the likelihood of false-positive results; rather, it often influences perceptions of risk rather than the test’s predictive ability.