Multiple pregnancy rates per ongoing pregnancy were @ % ( @/@ ) after in vitro fertilisation with single embryo transfer , @ % ( @/@ ) after in vitro fertilisation in a modified natural cycle , and @ % ( @/@ ) after intrauterine insemination with ovarian hyperstimulation ( one sided P = @ for in vitro fertilisation with single embryo transfer compared with intrauterine insemination with ovarian hyperstimulation ; one sided P = @ for in vitro fertilisation in a modified natural cycle compared with intrauterine insemination with controlled ovarian hyperstimulation ) .