Scientists from the Population Genetics and Identification Laboratory of the National University of Colombia confirmed the discovery of a case of heteropaternal superfertilization, a biological phenomenon in which a woman becomes pregnant by two different men in the same reproductive period. The identification process began in 2018, when a mother requested a paternity test for her two-year-old twin boys.
After performing DNA analysis with microsatellite marker technology, the Researchers determined that, although both children shared the maternal genetic profile, only one of them matched that of the alleged fatherrevealing the existence of two different parents for the same pregnancy.
Scientific verification process and methodology
In dialogue with BBC Mundo, Professor William Usaquén, director of the laboratory, confirmed that a microsatellite analysis protocol was applied. This procedure consists of extracting DNA from blood samples of the mother, minors and the alleged father, and then amplifying specific fragments using specialized equipment.
Through a technique called electrophoresis, Scientists converted genetic information into a numerical sequence that allows probabilistic comparisons to be made. In this particular case, 17 coincidence points were analyzed.
Paternity analysis is based on the comparison of between 15 and 22 microsatellite markers, which allows high levels of precision in genetic identification to be achieved.
As part of the protocol, the laboratory repeated the entire process from the beginning to rule out possible errors or contamination of the samples, obtaining the same result in both tests.
“I have been director of the laboratory for 26 years, and it is the first case we have seen, and so far the only one,” said William Usaquén.
Biological factors of superfertilization
The occurrence of this phenomenon requires a coincidence of low probability biological events. As Professor Usaquén explained, four simultaneous conditions must be met:
- Polyovulation: The release of two or more eggs in a single menstrual cycle.
- Multiple sexual partners in a close period.
- Temporal brevity between relationships.
- Successful fertilization of both eggs.
Specialists indicate that This process should occur in an approximate period of between 24 and 36 hours.which is the time during which the eggs remain viable after their release.
Even, In some cases, the eggs may be released hours or days apartwhich slightly increases the possibility of fertilizations at different times within the same cycle.
The experts clarified that this phenomenon is only possible in twin pregnancies (dizygotic) and never in identical twins.
An extremely rare phenomenon
According to scientific literature cited by the researchers, in an analysis of more than 39,000 paternity tests performed in the United States, only three cases of heteropaternal superfecundation were identified.
Despite their rarity, scientists warn that these cases could be under-reported, since most people do not undergo parentage testing.
This remains the only record of this type in the 26 years of history of the National University laboratory.
Impact and ethics in genetic research
Although scientific literature suggests that these cases could be detected more frequently due to the increase in DNA testing and the precision of molecular methods, the phenomenon remains exceptional.
Despite the scientific interest generated by the case, the Researchers stressed that ethics protocols prevent investigating the private lives of those involved.
“Affiliation tests are always done taking into account the integrity and privacy of the people,” explained Usaquén.
The study is strictly limited to the verification of affiliation profiles, guaranteeing the privacy and integrity of the family involved.