Heteropaternal Superfecundation: What Is It?

Heteropaternal superfecundation, the phenomenon of twins by different fathers, is an uncommon situation. Read this article to learn more.
Heteropaternal Superfecundation: What Is It?

Last update: 06 December, 2018

If you’re curious as to what heteropaternal superfecundation is, we recommend that you continue reading. It’s definitely an uncommon situation.

For this type of fertilization to occur, a number of factors have to come into play, including hyperovulation in women.

Heteropaternal superfecundation means the fertilization of more than one egg during the same cycle. That is to say that two eggs are fertilized by sperm from different men. This means that the woman will have twins, but not from the same father.

Meanwhile, hyperovulation refers to a condition in which two or more eggs are released during a cycle. Other necessary factors are superfetation and the participation of at least two sexual partners.

If only superfetation occurs, that means that both babies have the same father. Likewise, it’s possible that the woman releases more than one egg with only one (or none) being fertilized. There are many possible outcomes from this type of fertilization.

How does superfetation occur?

A woman may be ovulating more often than usual. Although it’s an uncommon process, it can happen naturally. In other words, the woman gets pregnant even though she’s already pregnant.

Heteropaternal Superfecundation

For most people, it’s an unexpected situation. However, the superfetation process means that it is in fact possible.

When a woman is undergoing fertility treatments, the stimulation is affected by means of hormones. These synthetic hormones help her produce more eggs. The more eggs that the woman releases, the greater the chances of becoming pregnant.

Current estimates say that approximately one in 13,000 fertilizations can result in heteropaternal superfecundation.

Specialists can identify a superfetation when they discover fetuses of different gestational ages. In other words, the fetuses have different characteristics, with one being more developed than the other.

While this can be evident while they’re still in the womb, it can also be discovered after delivery.

Heteropaternal Superfecundation

Cases of heteropaternal superfecundation

For the phenomenon of heteropaternal superfecundation to occur, several factors need to come into play. For this reason, it’s highly uncommon for it to occur spontaneously. It’s usually the product of a procedure supervised by medical and health care personnel.

In general, superfetation occurs within a few days. That is to say that the mother releases two eggs simultaneously, or within a few hours of each other. That’s why, in most cases, the differences become noticeable as the fetuses begin to grow.

Known cases have mostly resulted from the occurrence of sexual relations with different partners. This can include infidelity, polygamy, polyamory, rape, etc.

The are fewer than 10 known cases in the world of twins from different fathers. It is possible there are other cases, but the parents and/or twins are not aware of it, or do not wish to provide more information on the matter.

–Dinh Le Luong, Genetics Society of Vietnam

Case “A”

In 2009, a U.S. man discovered that one of his twins was not his child. The couple began to notice differences between the children, so they decided to get a DNA test. Finally, the mother explained that she had had sexual relations with another man.

Case “B”

Sometimes, the news is immediately apparent. For example, a doctor may discover that the babies have different gestational ages upon their birth. This was the case of a Vietnamese couple, whose twins were so different that they had a DNA test in order to confirm their suspicions.

Couples who have drastically different twins are more likely to think there was a mixup at the hospital, rather than think they’re the products of different fathers.

But as the expert notes, it may happen more frequently than we currently know, but the fathers may not be aware of the situation.

This text is provided for informational purposes only and does not replace consultation with a professional. If in doubt, consult your specialist.