While it was his first journey into an Italian political issue, the pope's support was not unexpected. Cardinal Camillo Ruini, the head of the Italian bishops' conference, is the pope's vicar for Rome.
The current law forbids sperm and egg donation, limits the number of embryos created with in vitro techniques to three, and bans all embryo research. Opponents of the law contend that it restricts scientific research and reproductive rights.
The referendum asks voters to repeal the law's provisions on embryo research, the three-embryo limit, the ban on egg or sperm donation from outside the couple, and any attribution of legal rights to the unborn.
The ANSA news agency reported that 85 percent of the physicians at Italy's largest gynecological hospital in Turin support changes to the law and that more than 100 of the doctors issued a public appeal yesterday for Italians to vote.
A communist politician, Franco Giordano, went on Radio Radicale and called the pope's remarks an ''unwarranted interference in the affairs of the Italian state."
The Vatican faced similar accusations of interference in church-backed referendums in 1974 and 1981 that unsuccessfully sought to overturn laws permitting divorce and abortion.
The bishops are pressing Italians not to vote in the hope that a low turnout will doom the proposed changes to the law. At least 50 percent plus one of eligible voters must cast ballots to make a referendum valid.
Benedict stressed that the family was ''fundamental" to Italian society. But he said that even in this overwhelmingly Roman Catholic country, the family has not been immune to secular trends.
''Even in Italy the family is exposed to the current cultural climate, therefore, to risks and threats that we all know," he said.
He cited the ''tendency of the culture to challenge the unique character and the mission of the family based on a man and a woman," a reference to acceptance in some countries to same-sex marriage.
