Forget what you know, you can actually get pregnant when you are already pregnant and that too with two different sperms! It is so rare that the doctors were pretty stumped.
About 2-3 years back a woman in Australia had two baby girls on the same day but they were not twins. Kate Hill’s 10-month-old daughters, Charlotte and Olivia, were conceived 10 days apart, that means Hill got pregnant when she was already pregnant. This phenomenon is known as “superfetation,” and it happens only when someone pregnant manages to conceive again.
This differs from identical twins as identical twins are born when one fertilized egg splits into two. Fraternal twins occur when two separate eggs are fertilized by two separate sperm. Even though it sounds similar to superfetation, fraternal twin embryos have same gestation period but the embryos conceived through superfetation aren’t.
Hill got pregnant on two different days and even though they were born on the same day, they had two different due dates. She says that her body had spontaneously released the egg when she was already pregnant and that led to the occurrence of this rare event. The couple said that they had conceived only once and the sperm had stayed for 10 days to fertilize the ova.
There are a few reasons why superfetation is so rare.
First of all, once you get pregnant your body is supposed to stop further ovulation. It means that there should not be a second egg and also that the ovulation occurs in every 28 days. And also the fact that they had sex once around that time suggests that his sperm had apparently lived for 10 days inside her before fertilizing another egg. That is unusual as sperm can live until 5 days inside the woman’s body.
Lastly, a mucus plug usually forms during pregnancy to prevent sperm from entering the cervix, and the uterine lining usually undergoes changes that make it unfavorable for a new embryo to be implanted.
One of the potential explanation lies in fertility treatments, Cackovic says. The lady was undergoing hormonal therapy due to her polycystic ovary syndrome, that can make it harder to get pregnant by messing with ovulation. “It is hypothesized that hormonal medications used for fertility treatments might alter these functions to enable this to occur, although it is unclear exactly how superfetation would then take place,” James says
The occurrence of superfecudity itself is a fascinating story.