Which of the following is a potential cause of spontaneous abortion?

Chronic maternal illness is indeed a recognized potential cause of spontaneous abortion. Conditions such as diabetes, hypertension, autoimmune disorders, and infections can negatively impact the pregnancy environment, leading to an increased risk of miscarriage. These chronic conditions may affect hormone levels, uterine health, or overall maternal health, all of which are crucial for maintaining a viable pregnancy.

In contrast, normal nutrition, positive mental health, and appropriate exercise are generally associated with healthier pregnancies. Adequate nutrition supports fetal development, positive mental health can contribute to a stable pregnancy environment, and regular, moderate exercise is typically encouraged for pregnant individuals unless contraindicated by specific health issues. Therefore, while chronic maternal illness can lead to complications, the other options contribute positively to pregnancy health.