Sperm imported into Israel from foreign donors causes more pregnancies than local sperm, according to a new study carried out by the Male Infertility and IVF Unit at Tel Aviv’s Asaf Harofeh Medical Center.

The study, which was presented at an Israeli Fertility Association conference last month, shows that 7.9 percent of women who were treated with foreign donor sperm got pregnant, as opposed to only 4.1 percent of IVF treatments that ended successfully with Israeli sperm. Artificial insemination showed similar results, with 9.1 percent success for foreign sperm, and only 6.4 percent for the local variety.

Researchers at Assaf Harofeh Medical Center examined 11,052 fertility treatments that used sperm from Israeli donors and 2,834 treatments that used donor seed imported from the United States over a period of 11 years. However, there were no conclusive reasons given for the findings.

Professor Arieh Raziel, the director of the hospital’s sperm bank, told Haaretz: “Our impression from laboratory tests is that the quality of imported and domestic sperm samples is similar. We assume that the difference must be related to the different populations of patients, since those requesting foreign sperm are generally younger.”

The study noted: “Imported donor sperm is elected in particular for open sperm donation and for religious reasons to eliminate the possibility of incest.”

Ultra-Orthodox fertility patients often request foreign sperm to eliminate the possibility of future incest. If a woman is treated with Israeli sperm, half-siblings could meet and marry, unknowingly, later in life.