seize

Definition

The term "seize" means to take or capture someone or something by force. It can also mean to overpower and control someone.

When a city was taken by means of military force, the soldiers would seize the valuable property of the people they had conquered.
When used figuratively, a person can be described as being "seized with fear." This means that the person was suddenly overcome with fear. It could also be translated as, "suddenly became very afraid."
In the context of labor pains that "seize" a woman, the meaning is that the pains are sudden and overpowering.