Transferring one embryo into women during in vitro fertilization (IVF) doesn’t lower their chances of giving birth but it does mean fewer women give birth to twins, with all the attendant health risks, a study said. IVF has traditionally involved transferring multiple embryos, which is known to increase by many times a woman’s chances of having twins and other multiple births, and raise risks to both mother and babies, including diabetes during pregnancy, premature birth and cerebral palsy.