Rabbi Eliezer Yehuda Waldenberg, one of the most respected halachic authorities of the modern era and a trailblazer in the field of Jewish medical ethics, passed away Tuesday at the age of 89. Waldenberg, who served on the High Rabbinic Court together with Rabbi Ovadia Yosef and Rabbi Yosef Shalom Elyashiv, was the unofficial rabbi of Sha'arei Tzedek and was perhaps best known for his controversial halachic opinion on abortions. In an opinion that sparked a caustic response by Rabbi Moshe Feinstein, Waldenberg ruled that it was permitted to abort a baby even as late as the seventh month in cases when the embryo suffered from Tay-Sachs, Rubella and even Down Syndrome. Unlike most halachic authorities, Waldenberg held that abortion performed by a Jew was not considered murder. Professor Avraham Steinberg, a pediatric neurologist and head of the Medical Ethics Center at Sha'arei Tzedek Hospital, as well as the editor of the Talmudic Encyclopedia, said that the uniqueness of Waldenberg's opinion on abortion was his willingness to permit abortions even when there was no danger to the mother. Another controversial ruling was Waldenberg's complete opposition to in-vitro fertilization (IVF). According to Waldenberg, the baby produced from IVF was not related to the biological mother and father and, therefore, did not fulfill the Torah injunction to "be fruitful and multiply." As a result, the removal of sperm for the purpose of IVF was prohibited. In addition to a 21-volume set of responsa entitled Tzitz Eliezer, Waldenberg also authored a book on the laws of sea travel on Shabbat called Shvita b'Yam, a book on mourning laws called Ein Ya'acov and a book on legal issues in the modern state called Hilchot Medina. Waldenberg got involved with medical ethics during the period that he served as rabbi of a synagogue adjacent to the old location of Sha'arei Tzedek Hospital in downtown Jerusalem. "Doctors who prayed at the synagogue, myself included, started asking him questions," recalled Steinberg. "Eventually, he began teaching a weekly medical ethics class for doctors and nurses." The questions Waldenberg answered were compiled in his Tzitz Eliezer. Thousands attended his funeral, which began at the Jerusalem's Etz Chaim Yeshiva. He is survived by his grandchildren.