Medical physiological point of view that the first child delivery of twins of women can have a second child, regardless of the first flat birth or caesarean section can have a second child, only the first child with twins of the mode of delivery of the next child delivery mode, interval time has an impact. If the first twin is delivered flat, the second child can be conceived after half a year, and the next child is recommended to be delivered flat; if the first child is delivered by caesarean section, the interval time should be 2-3 years, and the next child is recommended to be delivered by caesarean section. The main reasons for conceiving twins include genetic predisposition, ovulation stimulating drugs, and embryo transfer. Even if there is no gene for twins, the use of ovulation stimulating drugs and embryo transfer techniques can lead to the conception of two or more children.