Until recently, the use of IVF and other assisted reproduction methods has been linked to the multiple pregnancies. However, the rise of twins in the last decade made experts suspect there could be more to it. It was found that hormonal changes that take place in older mothers raise the chances of multiple pregnancies as well.

Researchers have shown that besides being less fertile, women after the age of 30 are more likely to produce more than one egg in the same menstrual cycle. This finding upset the researchers and proves previous theories that the rising levels of follicle-stimulating hormone that occur as women age can make ovaries work double and cause simultaneous double ovulation.

The fact that older women were found to be less fertile i.e. to produce smaller number of eggs but at the same time had an increase in dizygotic [non identical] twin rates was paradoxical and non explainable until now.
The production of more than one egg was found in women over the age of thirty as well as increase of FSH hormone, which was linked to multiple pregnancies. Multiple pregnancies are linked to greater rate of fetal death, miscarriage and premature births and this is why researchers recommend women not to delay their pregnancies in order to avid all the unnecessary complications.