In arguments Wednesday in a federal case challenging Utah's ban on gay marriage, the state argued that the ban nurtures a culture of “responsible procreation.”

Plaintiffs in the case are three gay couples who are asking a federal judge to declare invalid Amendment 3, the state's 2004 constitutional amendment limiting marriage to heterosexual couples.

The AP reported that about 100 people packed the Salt Lake City courtroom where the nearly 4-hour hearing was held.

U.S. District Judge Robert J. Shelby said that he hopes to hand down a decision in the case early next year.

Attorneys representing the state told Shelby that Utah is acting rationally to foster a culture of “responsible procreation.” They also argued that the law creates the “optimal mode of child-rearing.”

Stanford Purser of the Utah Attorney General's Office objected to plaintiffs' claims that the law is based on animus toward gay people.

“There is nothing unusual about what Utah is doing here,” he told Shelby. “That's the nature of legislation: You draw lines and make designations.”

“How is it by excluding same-sex couples from marrying you're increasing procreation?” Shelby asked.

Purser replied that the effects of allowing gay couples to marry remain unknown.

Nearly a decade before voters approved Amendment 3, Utah lawmakers approved the nation's first law prohibiting a state from recognizing the legal marriages of gay couples. Utah is also home to The Church of Jesus Christ of Latter-day Saints, the Mormons, which played a prominent role in passage of Proposition 8, California's now-defunct marriage ban.

The case was filed after the Supreme Court struck down the Defense of Marriage Act (DOMA), which led to federal recognition of the marriages of gay couples.