The likelihood of having more than one baby, i.e. a multiple pregnancy when fertilisation occurs naturally, depends on several factors. One of them is maternal age, as the older the woman gets, the higher the release of FSH hormone. This hormone helps to release more than one egg per menstrual cycle, which would increase the rate of multiple pregnancy.
In addition, family heredity also plays a role in multiple pregnancy. If there are cases of twin pregnancies or more babies in the mother's family, there is a high probability of recurrence.
On the other hand, race, maternal background, maternal weight and diet are also factors in the likelihood of a natural multiple pregnancy.