Answer:
1. Integumentary System
2. Digestive System and Endocrine System
Explanation:
An organ system combines multiple organs to perform one or more biological functions.
The integumentary system which human skin, is an organ system that protects the outer body. So the stretch marks women experience during pregnancy are evident on the skin, and since it was mentioned in the question that "A mother's body undergoes many changes to accommodate the developing fetus during pregnancy" it can be concluded that the skin stretched due to fetus development.
The digestive system here, the liver, can get disordered by a liver disease known as Cholestasis, which alters the flow of bile produced by the liver for digestion and can lead to bilirubin buildup poisoning blood and causing itchiness that can be experienced during pregnancy.
The Endocrine system is the Hormone center of the body, it affects the mood, and can cause itchiness too.
