Single embryo IVF safer than twins ISTANBUL, Turkey, July 9 (UPI) -- Births after the transfer of two embryos via in vitro fertilization had a 74 percent higher risk of death than a single embryo, Australian researchers say. Professor Elizabeth Sullivan of the University of New South Wales in Sydney and colleagues analyzed more than 50,000 births recorded in the Australian and New Zealand Assisted Reproduction Technology Database from 2004 to 2008. The study included 50,258 births of more than 20 weeks gestation and/or 400 grams -- 14 ounces -- birth weight following IVF pregnancies. Total perinatal deaths were defined as the number of fetal deaths, or stillbirths, plus the number of neonatal deaths, deaths that occur before 28 days after birth. The study found an overall perinatal mortality rate of 16.2 per 1,000 births, representing 813 perinatal deaths during the study period -- 630 stillbirths and 183 neonatal deaths. Sullivan said twins accounted for half the total neonatal deaths and one-third the perinatal deaths. Twins also had significantly higher perinatal mortality rate than singletons, or single births -- 27.8 per 1,000 births and 12.4 per 1,000 births. "The number of embryos transferred per procedure is the major determinant of multiple pregnancy and multiple delivery, which contribute to an elevated risk of preterm birth and low birth weight," Sullivan said in a statement. These are risks in addition to those already faced by women being treated for infertility. The findings were presented at the annual meeting of the European Society of Human Reproduction and Embryology in Istanbul, Turkey.