Which factor significantly increases the risk for a Down syndrome infant?

Maternal age older than 35 years is a significant risk factor for having an infant with Down syndrome. As women age, the risk of chromosomal abnormalities, including Down syndrome (Trisomy 21), increases due to factors related to the aging of oocytes (eggs). The age-related decline in cellular processes, along with the increased likelihood of nondisjunction during meiosis, contributes to this heightened risk.

Research has consistently shown that the incidence of Down syndrome rises with maternal age, particularly after the age of 35. Consequently, many healthcare providers recommend additional prenatal screening and diagnostic options for women who are pregnant at or beyond this age.

The other options, while they may hold some relevance in certain contexts, do not convey the same level of risk association as maternal age older than 35. For instance, while a family history of Down syndrome might suggest a potential for recurrence, it is not as strongly correlated with risk as maternal age. Maternal age younger than 16 and a positive family history of genetic disease, while important factors in genetic counseling, do not particularly influence the risk of Down syndrome in the same significant manner.