Could the increased amount of multi births effect the evolution of the female body

by the uterus becoming larger to accommodate the two or more fetuses?

note that if you comment you will be cited in a paper regarding this topic so I would prefer if someone with medical expertise could answer this and leave your qualifications/occupation that initials you to give your opinion.

One thing you need to understand about evolution is that it is the ones who have adapted first and don't die that pass their characteristics on to the next generation.

In other words, if some women had larger uteruses and it turned out that, as a result of an increased number of multiple births, the mortality rate of women with smaller uteruses increased, then the women with larger uteruses would be the ones who would successfully pass on their genes and it would affect the evolution of women.

It sounds backward that the adaptation (or probably more correctly, the mutation) has to occur before the condition (a large number of multiple births, in this case) in order for the evolutionary process to work, but that's the way it is.

To put it another way, an increase in multiple births will NOT, on its own, cause women to grow a larger uterus over generations. But if the number of multiple births increases and some women have larger uteruses that allow them to give birth more successfully, while those with smaller uteruses experience birth complications leading to their own death or an increase in infant mortality, then the women with a larger uterus will be more successful at reproducing and that trait will tend to be passed on.