One year ago, the reportedly "fastest-growing church in Africa" dedicated a $15.5 million, 10,000-seat conference center in a sparse prairie town northeast of Dallas whose population is less than 1 percent black.

The auditorium was just the beginning, said officials with the Redeemed Christian Church of God (RCCG)—a fish farm, schools, and a university were on the way. The church is offering free land to members willing to build a home on the 788-acre campus, and plans to expand its Pavilion Center to seat 1 million.

It sounded audacious, but then so did its statistics: The Pentecostal denomination that started in Nigeria in 1952 opened its first American congregation in Detroit in 1992. Between 2009 and 2013, it nearly doubled its churches in North America to 720.

But when the RCCG's longtime leader, Enoch Adejare Adeboye, returns for the North American branch's convention in June, not much will have changed. Doyin Oke, chief operating officer, says the RCCG has about the same number of North American churches it did a year ago.

101 Babies born at last year's weeklong convention in Nigeria.

Church planting, however, is not RCCG's only strategy for growth. Even among West Africans, who have some of the highest birth rates in the world, the RCCG has a reputation for promoting baby-making among its members. (The World Bank says Nigeria has 40 births per year per 1,000 people; the United States has 14.)

In 2011, as Adeboye neared age 70, he asked that RCCG give him a birthday present of adding 70,000 babies to the church. He later raised the goal to 100,000. (He also called RCCG to make 700,000 new converts.)

"If I had my way, I would have had 100 children," Adeboye told convention-goers, according to Nigerian newspaper Vanguard. "But I thank God; he is now giving thousands of babies because he knows my love for babies."

The Nigeria annual convention keeps a running tally of the babies born at the convention itself over its eight days. Last year it hit 101.

Oke says the North American branch "also rejoices when families are blessed with children, because 'happy is the man that hath his quiver full of them'" (Ps. 127:5, KJV). James Adekunle, an RCCG pastor in Nigeria, said having children is simply obeying the Genesis mandate to multiply and conquer the earth. He also says that "every Christian has a responsibility to have as many children as possible."

Even for Nigerian Christians outside the RCCG, having many babies is a way to preserve Christianity. "Today there exists demographic warfare by certain elements within the Muslim community who see this as a means of Islamization," says Gideon Para-Mallam, regional secretary for the International Fellowship of Evangelical Students. "This is a global reality we cannot ignore."

The average fertility rate among Muslims in Nigeria is between six and seven children per woman, while non-Muslim women have five children on average, according to the Pew Research Center.

Not all Nigerian Christians think out-birthing Muslims is the answer, however. "It's not about how many [children] we have but how we train the few we have," says Francis Bola Akin-John, president of International Church Growth Ministries.

Impoverished Christians should not have more children than they can afford, he said. "Of what use is giving birth to children into poverty? If we don't disciple and train them, they will be converted to Islam."

Praises Omole, a doctor and member of the Methodist Church Nigeria, disagrees. "It's not our business to figure out how those children will be fed," he says. "Ours is simply to trust God and obey him."

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