As unbelievable as it might be, a woman can become pregnant while already being pregnant. It sounds like a supernatural phenomenon from a sci-fi movie, but it’s true — a woman can conceive again after already being pregnant.
We became interested in this topic and studied it carefully to eventually present you with the final results.
This rare condition is called “superfetation,” which implies the conception of a second fetus while being pregnant with another one. As a result, a happy mother gets 2 twins with different gestational ages and sometimes even 2 different dates of birth.
Superfetation is not the same thing as superfecundation. The latter implies the fertilization of 2 eggs released during one menstrual period from separate intercourses. In this case, a woman will end up having vitelline or bicyclic twins. In the case of superfetation, a woman conceives during different menstrual periods and apart from the gestational age, the twins will have different weights, heights, and even blood types.
Normally, when a woman is pregnant her ovaries stop releasing eggs to the uterus because the hormones send a signal to the body to “get prepared” for growing a baby. However, when superfetation takes place, ovaries generate and release another egg, which might also get fertilized.
There are 10 officially known cases of this phenomenon and the last one happened in Australia with a woman named Kate Hill — she became pregnant twice within 10 days. She gave birth to 2 baby girls — Charlotte and Olivia, who have been classified as twins, however, the time difference between their conception was 10 days. Though they were born on the same day, their weights and blood types were different.
Superfetation can occur among animals as well. Mice, kangaroos, rabbits, felines, and sheep have all been claimed to be subject to superfetation. Fish have demonstrated this remarkable ability as well.
It was Aristotle who first noted this phenomenon in rabbits. He observed that in the litters rabbits had given birth to the babies were different sizes — the younger ones were significantly smaller in size. This was the result of superfetation, where the younger offspring was smaller due to the occurrence of the second pregnancy.