He should've told you. He wished he hadn't been scared to break your heart. He had been a coward and now you were paying the price. He didn't think this would be a problem so soon. He thought you two had time before children came into the picture. Yet, now you were pregnant and you were over the moon. But everyone else knew this wasn't entirely joyful news. You were high fae and both Cassian and the babe in your womb were illyrian.
When you discovered the baby had wings you were overjoyed, imagining Cassian teaching your child how to fly. You were oblivious to the stress and anxiety gnawing away at Cassian and the others. Your body would struggle to deliver the baby when the time came, the baby would likely become stuck, and the risks to both yours and the baby's life were very high.
Cassian watched you smile as you caressed your bump and hung baby clothes in the wardrobe. He desperately wanted to be honest with you, but he worried if the stress would make you sick in this state, and he didn't want to take away your joy and excitement. But it was your body, and therefore you deserved to know.