For generations, Catholic women have been the foundation of the church, filling the pews, doing much of the volunteer work that keeps parishes running and passing on the faith to future generations.
But the day of reckoning for a church that excludes women from the priesthood and has alienated many with its emphasis on rules governing sexual morality may finally have come.
What once was a large gender gap in church attendance is gone, and the latest research indicates Catholic women may be no more likely than Catholic men to say the church is among the most important parts of their lives or that they would never leave the church.
"It's troubling," said Mary Gautier of the Center for Applied Research in the Apostolate at Georgetown University. "The difference between men and women is just gone."
And it may get worse, some researchers say.
Women up until the late Baby Boomers, those in their 60s and beyond, can disagree with the church, but "they cannot not be Catholics," said sociologist Patricia Wittberg of Indiana University-Purdue University in Indianapolis.
But non-Hispanic Catholic millennials, raised in a more assimilated culture where Catholicism is not as strong a part of their identity, have fewer ties that bind.
"There is emerging evidence that women's longstanding loyalty to the church can no longer be taken for granted," researchers William D'Antonio of Catholic University of America, Michele Dillon of the University of New Hampshire and Gautier state in their new book, American Catholics in Transition.
It may take a pope to make a difference.
The turning tide
Religious women in the United States still find leadership roles in most Christian congregations hard to come by -- fewer than 10 percent of all U.S. congregations are led by a woman, according to the 2006-2007 National Congregations Study. But women have been and continue to be a cornerstone of faith.
Women are more likely than men to pray daily, attend services frequently, say religion is very important in their lives and have absolutely certain belief in a personal God, according to the Pew Forum's U.S. Religious Landscape Survey.
Six in ten people in the pews are women, according to the 2008-2009 U.S. Congregational Life Survey. Just 2 percent of congregations do not have more women than men.
The gender differences have historically also been significant in the Catholic Church.
"For several decades, women have been able to maintain an active loyalty to Catholicism and to live with the irony presented by the twin realities of their commitment to and marginalization within the church," D'Antonio, Dillon and Gautier noted.
But the milestone findings they present from five studies as part of the American Catholic Laity Project, a national survey taken every six years since 1987, suggests this is no longer true.
Consider the rapid declines in commitment among women, while men's level of commitment remained fairly steady:
• In 1987, women were almost 50 percent more likely to attend weekly Mass, with 52 percent of women and 35 percent of men attending regularly. In the 2011 survey, less than a third of Catholic women, the same proportion as men, reported attending weekly Mass.
• In 1987, 58 percent of women, compared to 39 percent of men, said the Catholic Church was among the most important parts of their lives. By 1993, the percentage dropped to 49 percent for women and 37 percent for men. In 2011, just 35 percent of women and men ranked the church as one of the most important parts of their lives.
• The percentage of women who said they would never leave the Catholic Church declined from 61 percent in 1987 to 55 percent in 2011, while the percentage of men claiming such loyalty rose from 50 percent in 1987 to 56 percent in 2011.
Wittberg says she has found similar evidence of the disappearing gender gap in her research using General Social Survey data.
A related concern for Catholics is a significant decline in baptisms. From 1995 to 2004, there was about one Catholic infant baptism for every four U.S. births. After 2004, the percentage began to drop, with about one Catholic infant baptism for every five births, the Center for Applied Research in the Apostolate reported.
"It's the women that insist the babies be baptized," Wittberg noted.
Can one man make a difference?
The future is difficult to predict.
Catholic commitment among women could plateau or increase. Hispanic Catholic women, a fast-growing demographic, show higher levels of commitment.
Women may be excluded from the priesthood, but they are gaining increasingly influential roles in other aspects of church life; four in five lay ecclesial ministers are women.
Yet, while there are no definitive answers as to why the commitment of Catholic women is in a steep decline, some researchers note cultural shifts toward more personal autonomy in moral decision making and disagreement over issues from women priests to homosexuality may be significant factors.
Many young Catholic women today get their impressions of Catholicism more from mainstream media than the church, Wittberg said. And those public images often portray the church as oppressing women, in part because of the ban on female clergy.
Dillon said many Catholic women find much to appreciate in the church's spirituality and culture, but are "turned off by the constant beating of the drums" on issues such as homosexuality and contraception, and are frustrated by being unable to be full participants in the church.
How can the church reach out to Catholic women?
Toning down the emphasis on rules, and embracing a loving attitude that lifts up social justice issues -- a particular concern of Hispanics -- "will go a long way" to help, Dillon said.
In this regard, many observers say Pope Francis sent out a positive signal with his recent remarks that "the thing the church needs most today is the ability to heal wounds and to warm the hearts of the faithful; it needs nearness, proximity.
The church sometimes has locked itself up in small things, in small-minded rules. The most important thing is the first proclamation: Jesus Christ has saved you. And the ministers of the church must be ministers of mercy above all.
Those words, Dillon said, "will go some way to make a lot of women - and men - feel more positive about the church."
Some three decades ago, the U.S. Catholic bishops began drafting a pastoral letter on women, holding listening sessions in dioceses around the country. Nine years later, they still could not reach agreement, with some bishops lamenting that Vatican-sponsored revisions to the proposed document would do more harm than good.
This time around, it is the pope who may be listening.