Which of the following is not considered a high-risk pregnancy?

A) History of infertility
B) Very young mother
C) Very old mother
D) Single mother

While being a single mother may present its own unique challenges, it is not inherently considered a high-risk pregnancy. A history of infertility, a very young or very old mother, and other factors such as medical conditions or previous pregnancy complications are more commonly associated with high-risk pregnancies.