Can you have two pairs of twins in one pregnancy?
If females can produce two egg cells at times, then two sperm cells create fraternal twins, can they split into two pairs of the same fraternal twins?
Kat - This is possible, yes. Quadruplets, that's a pregnancy with four babies, can happen in lots of different ways. You could get four different eggs fertilised, one egg might split into four, that would result into four identical quads, you could get one egg splitting into three, one egg being fertilised, two fertilised eggs splitting into two, all sorts of variations on this. Now, I can find two cases of double twins that I found out about. There's a set of quads made up of two pairs of girls, so that's two fraternal pairs of identical girls, born in the UK in 2010 and a pair of identical boys and a pair of identical girls born Canada in 2008. Both of these resulted from IVF treatment where the woman was implanted with two fertilised embryos and then these both split into two, creating two pairs of twins. Now, this is an extremely rare situation and natural quadruplet pregnancy is extremely rare, so it is possible that it could happen naturally, but it would be very unlikely occurrence.