Take, for example, the Sisters of Life, the religious order of Sister Virginia Joy. Many of the nuns are in their 20s or 30s and have a commitment that can be divisive even in the Roman Catholic Church: “promoting life,” which in practice includes an emphasis on discouraging abortions.

The members may hold to traditional teachings, but as they see it, there is nothing more countercultural in 2015 than a young woman’s becoming a nun — eschewing careerism, material possessions, sex. Two other traditionalist orders — a Dominican order in Nashville, and one in Ann Arbor, Mich., which has expanded to Austin, Tex. — have attracted national attention; in 2010, the Ann Arbor nuns even made it on “Oprah.”

Margaret Guider, a Franciscan nun who teaches at Boston College, said young women were attracted to these orders not by any one political slant but by an old-fashioned sense of focus and identity. Where many religious orders now allow nuns to choose their dress, or their career, these groups dress alike, pray often together and all work in one field, be it as schoolteachers or in anti-abortionactivism.

“What characterizes those groups is they tend to have maintained what I would call a conventual life,” Dr. Guider said. “They live in convents or designated communities, they tend to have a traditional habit and they tend to have a very focused ministry. Their life has a real focus and continuity that holds the whole group together all of the time.”

All of the 84 Sisters of Life have joined since 1991, when Cardinal John J. O’Connor, who was the archbishop of New York, founded the order. Ten postulants, or first-year members, are expected in September. On Thursday, at the order’s retreat center in Stamford, Conn., eight sisters professed “final vows,” making a commitment for life. To the traditional vows of poverty, chastity and obedience, the Sisters of Life add a fourth vow, “to protect and enhance the sacredness of every human life.”