Causes of insomnia in the second trimester. The second trimester is one of the important periods of pregnancy, and insomnia often troubles many pregnant women. Understanding the causes of insomnia is very important to alleviate the problem. Let’s analyze the causes of insomnia in the second trimester from four aspects. Hormonal changes Changes in hormonal levels during pregnancy are one of the main causes of insomnia in pregnant women. During the second trimester, progesterone