Atheism and IQMormons may also have some immunity the detrimental effect IQ on fertility. In the general population increasing income (highly correlated with IQ) is associated with both declining fertility and declining religious commitment. In Mormons the reverse is true.
Mormon fertility is positively correlated with income and Mormons with higher levels of formal education tend to be more religiously committed.
On multiple religious measures Mormons stand out for having exceptionally high levels of religious commitment. More than nine-in-ten Mormons report a belief in God and that the Bible is the word of God. Mormons are also very observant in their religious practices with more than eight-in-ten praying daily. Mormons strongly support a strict interpretation of their faith and the preservation of traditional beliefs and practices.
From my experience of a best friend who is Mormon in the UK, I can only say that she was highly motivated to find a fellow Morman guy to marry and had a criteria of being very religious, fit and attractive but also wealthy. She said that her motivation for a wealthy husband was not standard greed (as this was anathema to her religious views) but was mostly due to their want/need to give the church 10% of their earnings straight from their wages. The fact she wanted a fit and healthy husband was also in part due to her wanting to have a large family and needing a husband who could not only provide financially for that but also to help keep up with the strains of a large household.