And many Mormon women today take that charge seriously. They feel comfortable and respected for doing so during various church services, including the sacrament worship meeting, Relief Society (for adult women), Young Women (for teen girls) and Primary (for children). African women, for example, routinely and without embarrassment suckle their babies at church, undeterred by the presence of American missionaries. One Utah woman sang in the choir during her LDS stake conference (regional meeting) and often directed the music in her own ward while her baby, in a sling, quietly slurped away.
Indeed, Utah, with its predominant Mormon faith, has one of the highest percentages of breast-feeding moms in the nation, according to a 2012 report card from the Centers for Disease Control and Prevention. Nearly 86 percent of children are breast-fed at some point, with 64.4 percent still nursing at 6 months, compared with 47.2 percent nationwide.
In recent years, however, some Mormon moms in and out of the Beehive State have faced criticism, gossip and even reprimands from church leaders for "not completely covering up."
As a new mother in Provo about three years ago, Heather Moore-Farley got a call from her Relief Society president, asking her to use a blanket or go to the mothers' lounge in the women's bathroom to breast-feed to protect others' sensitivities. Then her bishop suggested Moore-Farley and her husband pray about it. They did and got the same answer: She was doing nothing wrong.
Sometime later, another ward member confronted the couple as they were walking home from church and accused her of "contributing to the pornography problem" and "not keeping [her] covenants."
Moore-Farley felt hurt and angry, but it didn't change her mind about breast-feeding. She began to collect stories like hers from other Mormon moms. The couple eventually moved to the Bay Area and had no more trouble nursing subsequent children at church.
Verbal attacks on lactating mothers from many backgrounds, though, have continued even as proponents have grown more vocal and better organized in defense of their rights.
They have staged "latch-on" protests (or "nurse-ins") at places such as Target stores, Facebook headquarters and the national mall that ejected women from their premises for breast-feeding.
Now a similar effort is under way among Mormon women known as Latter-day Lactivists.
"We represent the rights of LDS women to breast-feed their children in their ward houses. We stand for the rights of mothers to feed their babies where, when, why and how they may," the group's statement of purpose reads. "We maintain that it is neither immodest nor immoral for a woman to breast-feed her child as openly as she pleases. We maintain that mothers have the right to be safe from discipline, discrimination and persecution for nursing in public."
These activists are not planning any public rallies but are asking LDS leaders to add a line to the church's leadership instruction manual, known as the Handbook, which currently makes no mention of breast-feeding.
LDS Church spokesman Scott Trotter did not comment on whether Mormon leaders are or would consider mentioning it, but he did say that "countless thousands of mothers have been accommodated in church for generations, simply by everyone observing common sense, discretion and respect."
Any change would come too late for Marie Le, who stopped attending LDS services after being scolded in 2006 for breast-feeding her baby.
Though Le says "nothing was showing," the Idaho mother got a visit from her Relief Society president, who said that some women had complained about her nursing, that she was harming their husbands who had "porn problems" and that they didn't want their teenage sons "exposed to anything."
Le went to her Mormon bishop, who she says sided with the critics.
The experience was "emotionally devastating," Le recalls. "I felt that church was like a big family and now my safe religious haven had betrayed me."
She started having panic attacks at the thought of a whispering campaign about her. Le no longer considers herself a Mormon.
Jenne Erigero Alderks, founder of the blog Birthing in Zion, doesn't want to see this happen to any other women.
Alderks, a Mormon in the Seattle area, has been talking with her LDS stake president and Relief Society leader about the issue's impact on women throughout the 14 million-member Church of Jesus Christ of Latter-day Saints. She, too, hopes for a faithwide policy celebrating breast-feeding women at church. She acknowledges it's largely a U.S. cultural problem, but wants to see it addressed in a universal way.
The Mormon mom says she has been careful and discreet when nursing her babies, uncovering and covering again quickly, but she won't use a blanket or go to an isolated area. "Why should I have to leave and miss out on activities and talks just because I am a good mother?"
What about single mothers or those whose husbands are sitting on the stand or engaged in other church responsibilities? Should they leave their toddlers or other children while they go to the lounge?
One of the issues, Alderks says, is common Mormon views of female bodies and modesty.
"If a man sees me breast-feeding and is thinking sexually, it's his problem," she says. "My husband says there's nothing sexy about it."
If motherhood is an LDS woman's highest calling, she says, "get out of our way, and let us follow our conscience on how best to do that."