If PAPP-A levels are low, which trisomies could be indicated?

Low levels of PAPP-A (Pregnancy-Associated Plasma Protein A) during the first trimester of pregnancy have been associated with an increased risk of several chromosomal abnormalities, particularly aneuploidies. Specifically, research indicates that low PAPP-A levels are linked to trisomy 21 (Down syndrome) and trisomy 18 (Edwards syndrome).

Trisomy 21 is the most common chromosomal condition related to low PAPP-A levels. However, studies have also demonstrated that low levels can be indicative of trisomy 18, which is associated with more severe developmental issues and typically results in a higher likelihood of miscarriage or neonatal death.

While low PAPP-A can be an indicator for trisomy 21 and trisomy 18, it does not show the same correlation with trisomy 13 (Patau syndrome) in the majority of screening studies. This is why the correct answer encompasses trisomy 21 and trisomy 18, as both are recognized in clinical practice as conditions that may be indicated by low PAPP-A levels. Thus, option C accurately includes the relevant trisomies associated with low PAPP-A levels.