She said, “In humans, it is very rare. In fact, in the whole medical literature, what has been recorded is less than 10 cases. It is more common in certain animals like rodents, fishes, kangaroos.”
She stated that the condition occurs when a woman ovulates in two different cycles and releases two different eggs. According to her, these eggs get fertilised and implantation occurs in the uterus.
Ogunro added, “Basically, what happens is that a woman ovulates, she releases her eggs and then the egg gets fertilised and implanted in the uterus, so pregnancy occurs and then in another cycle, she ovulates again, releases the eggs, they get fertilised and implantation occurs for the second time.
“It is extremely rare because the way nature does is that once a woman is pregnant, it’s rare for another pregnancy to occur.
“That is because the pregnancy hormones act as a barrier to prevent another pregnancy and also, the lining of the womb undergoes changes that it is almost impossible for a second pregnancy to occur, however, this rare condition can occur.”
According to the expert, in a case where superfetation occurs, both babies can survive although one would be older than the other.
She further explained the difference between twins and superfetation saying, “With twins, what happens is that they are conceived at the same time, within the same menstrual cycle but with superfetation, it is at different times, one is older than the other.
“What happens is that if one is older than the other, the younger one may be delivered pre-term.
“The younger one has all the challenges in pre-term, challenges such as being born earlier than the due date. It is different from twins because with twins, the conception takes place at the same time but with superfetation, it is two eggs that have been released and fertilised at different times in two different menstrual cycles.”
Ogunro stressed that the condition is extremely rare in humans, so it is not something women should bother or be worried about.
According to a 2017 study, first published in the Journal of Reproduction & Sexual Health, “Superfetation in humans is an extremely rare situation in which a woman becomes pregnant a second time with another younger foetus in the face of an ongoing pregnancy.
“It is claimed to be common in some species of animals but is extremely rare in humans that fewer than 10 cases have been reported in the medical literature. Superfetation is different from the process of twinning or multiple gestations and involves the conception of an additional fetus during an established pregnancy.
“With superfetation, the two fetuses have different gestational ages and due dates.”
The study explained that “after conception occurs in a normal pregnancy, hormones have released that stop further ovulation.
“The lining of the uterus thickens in a way that should prevent a second embryo from attaching itself.
“Finally, the cervix forms a barrier known as the mucus plus, which is designed to protect the developing fetus from microbial infection and serves as an effective barrier to sperm.”
The study carried out in the department of obstetrics and gynaecology at Delta State University, Abraka, Nigeria, stated that superfetation is so unlikely because “three near-impossible things need to happen in order for it to occur; ovulation must occur while a woman is already pregnant, sperm must somehow make it past the mucus plug, and implantation must occur in a uterus that is no longer prepared for it.
“The odds of all three of them happening are without a doubt extremely small as reflected by the very occasional reports of superfetation in humans in the medical literature.”
Source: healthwise
