A more thorough explanation:

Definition: Plead (one's) belly is a historical slang term used to describe a female defendant's claim of pregnancy as a defense to avoid a court's sentence of capital punishment or transportation.

In the past, if a woman was accused of a crime that carried the death penalty or transportation, she could plead her belly to avoid punishment. This meant that she claimed to be pregnant, and a jury of matrons (married mothers) would be appointed to examine her claim. If the woman was found to be "quick with child" (in an advanced state of pregnancy), she would be granted a reprieve until after the child's birth or miscarriage.

For example, if a woman was accused of theft and faced the death penalty, she could plead her belly to avoid punishment. If the jury of matrons found her to be pregnant, she would be granted a reprieve until after the child's birth.

However, if the woman was found to be lying about her pregnancy, she would be punished severely. The court would keep track of her to see if the delay was justified or if she should be made to suffer the sentence at the next session.

Although the plea and the special jury are no longer in use, the prohibition against executing a pregnant woman persists in modern law.

For example, in the United States, it is illegal to execute a pregnant woman under 18 USCA § 3596(b).