WARSAW, Poland (AP) — In an unprecedented move, the Vatican on Sunday is beatifying a Polish family of nine — a married couple and their small children — who were executed by the Nazis during World War II for sheltering Jews.

Last year, Pope Francis pronounced the deeply Catholic Ulma family, including the child that Wiktoria Ulma was pregnant with, martyrs for the faith, paving the way for the beatification Mass that is taking place in their home village of Markowa, in southeastern Poland.

The Ulmas were killed at home by German Nazi troops and by Nazi-controlled local police in the small hours of March 24, 1944, together with the eight Jews they were hiding at home, after they were apparently betrayed.

Jozef Ulma, 44, was a farmer, Catholic activist and amateur photographer who documented family and village life. He lived with his 31-year-old wife Wiktoria; their daughters Stanislawa, 7; Barbara, 6; Maria, 18 months; and sons Wladyslaw, 5; Franciszek, 3; and Antoni, 2.

With them were killed 70-year-old Saul Goldman with his sons Baruch, Mechel, Joachim and Mojzesz, along with Golda Grunfeld and her sister Lea Didner with her little daughter Reszla, according to Poland’s state Institute of National Remembrance, IPN, which has meticulously documented the Ulmas’ story.

The Catholic Church faced a dilemma in beatifying Wiktoria’s unborn child and declaring it a martyr because, among other things, it had not been baptized, which is a requirement for beatification.

The Vatican’s Dicastery for the Causes of Saints issued a clarification saying the child was actually born during the horror of the killings and received “baptism by blood” of its martyred mother.

The clarification was issued Sept. 5 by Cardinal Marcello Semeraro, the prefect of the Vatican’s saint-making office. Semeraro is presiding over the beatification Mass, at which more than 30,000 participants from across Poland are expected. It is the first time that an entire family is being beatified.

Poland’s conservative ruling party has been stressing family values and also the heroism of Poles during the war and the beatification ceremony is a welcome addition to its intense political campaigning ahead of the Oct. 15 parliamentary elections in which the Law and Justice party wants to win an unprecedented third term.

The Ulma beatification poses several new theological concepts about the Catholic Church’s ideas of saints and martyrs that also have implications for the pro-life movement because of the baby in the mother’s womb, said the Rev. Robert Gahl, a professor of ethics at the Catholic University of America and Rome’s Pontifical Holy Cross University.

Perhaps because the concept of “beatification of a fetus” could be weaponized by the pro-life movement, the Vatican apparently felt it necessary to state that the child was “born” at the moment the mother was executed.

By stating that the child was actually born, the Vatican also affirmed that the killers intended to kill the child out of hatred for the faith, a requirement for a martyrdom and beatification declaration, Gahl told The Associated Press.

After beatification, a miracle attributed to the Ulmas’ intercession would be necessary for their eventual canonization, as the church’s sainthood process is called.

Israel’s Yad Vashem Institute in 1995 recognized the Ulmas as Righteous Among Nations who gave their lives trying to save Jews during the Holocaust.

In Poland, they are a symbol of the bravery of thousands of Poles who took the utmost risk while helping Jews. By the occupying Nazis’ decree, any assistance to Jews was punished with summary execution. A Museum of Poles Saving Jews During World War II was opened in Markowa in 2016.

Poland was the first country to be invaded by Nazi Germany, on Sept. 1, 1939. Some 6 million of its citizens were killed during the war, half of them Jews.

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Associated Press writer Nicole Winfield in Rome contributed to this report.