What is superficiality, or superfluous pregnancy?

Superficiality, the fact of getting pregnant when you are already pregnant, is a blessing for medical television series, inevitably creating situations that lend themselves to fiction. But what about in reality? What is it exactly? Is this possible in humans? We take stock of this pregnancy of two children who are not twins!

Superficiality: Getting Pregnant While Pregnant

The superficiality would be the result of get pregnant … when you already are ! The press has repeatedly echoed the stories of women who experienced this situation, carrying two babies who are not twins, from a different egg, a different sperm, or even a sperm. ‘another man. In the medical literature, these cases are extremely rare, around ten cases have been identified in all in the world. 

If the medical profession wonders about the possibility of a superfluous pregnancy in humans, it notes that certain situations could favor it:

• a uterine malformation
• stimulation of the placental production of chorionic gonadotropic hormone (hCG) linked to a particular genetic mechanism, triggering a new ovulation and allowing a second implantation
• an ongoing process of IVF (in vitro fertilization) 

Is it possible to get pregnant when you are already pregnant?

In humans, it is usually not not possible to get pregnant when you are already pregnant. This is because the properties of the uterus mean that there cannot be a second implantation when a pregnancy has already been implanted. Modifying endometrial cells to prepare for pregnancy normally prevents further implantation.

« We have of course heard of the few cases of superfluous pregnancy in humans in the medical literature – which have often been publicized – but it is an extremely rare process that is not supposed to happen ! », Notes Nathalie Boileau, gynecologist in medical and obstetrics at the Clinique des Émailleurs, in Limoges.

Explanation: can we ovulate at the start of pregnancy?

Normally, once an egg has been fertilized by a sperm, the uterine walls thicken in order toprevent a second embryo from attaching to it, and hormonal changes stop new ovulations. We therefore stop ovulating as soon as we are at the start of pregnancy.

In the case of a twin pregnancy, either there is fertilization of an egg by a sperm then the egg divides in two: the twins will then look very similar and will be of the same sex, this is what we call monozygotic twins or “identical twins”. In the case of dizygotic twins or “fraternal twins”, two eggs were produced and each was fertilized by a sperm. The two babies can then be different sex and less alike, just like siblings. 

Where the superficiality is extraordinary is that it seems that the second ovum is not not emitted at the same time, or even in the same menstrual cycle ! A new sperm would fertilize this new egg, which would manage to hang on despite the presence of another fertilized egg for several days, or even weeks … It would then be possible that two embryos that are not twins are developing at the same time!

Definitions: superfertilization or superficiality?

Superfertilization is also a rare phenomenon which concerns one in 13 pregnancies, but which is becoming more frequent with the growing recourse in Western countries to medically assisted procreation. Superfertilization consists of fertilization of two eggs by two spermatozoa during the same cycle, but not during the same intercourse.

Here again, it is in itself possible that fathers are different (we speak of heteropaternal superfertilization. Nineteen cases have been reported in all the world medical literature.

Superfertilization usually goes unnoticed, because the small time difference between the two fertilizations is reminiscent of a twin pregnancy with “fraternal twins”. 

Superficiality, more common in other animals than in humans

While most mammals cannot induce pregnancy when another has already started, this is not the case, for example, with hares and badgers. The hase, female of the hare, can indeed be fertilized before giving birth, on average 3 to 7 days before giving birth to his legs.

The badger (female badger), on the other hand, is used to superfluous pregnancies and even favors different fathers in order to prevent badgers from killing their young. In addition, some fish can also experience superfluous pregnancies.

What are the risks of a superfluous pregnancy in women and babies?

Extremely rare, superfluous pregnancy does not seem no particular risks for the woman or for her future babies. ” The pregnancy proceeds, past this atypical and questioned conception, like a twin pregnancy», Indicates Nathalie Boileau. In the ten or so cases reported by the world medical literature, the difference was in any case not large enough for the youngest baby to be in danger.