Yes this has been proved earlier, it happened somewhere in US(not sure) where a baby was pregnant while she took birth.
sarcasm fail =)I dnt think so its possible, coz first of all how will the sperm enter the baby,
i dnt think sperm is so wise to go via the v-g-i-na
And to get pregnant, she need to have a full developed uterus, ovaries etc etc
So, not possible