Cincinnati, OH. U.S.A. December 13, 2005 — DNA Diagnostics Center (DDC), a leading DNA testing company, reports several cases of twins that DNA paternity testing proved to have different fathers. Such occurrences, although rare, are being more frequently revealed via DNA testing.

“These cases underline the necessity for testing both fraternal twins in a paternity test, if any doubt at all exists about the circumstances surrounding the twins’ conception,” says Dr. Michael Baird, DDC’s laboratory director. Paternity test results are often used as basis for child support and child custody decisions. Further, the biological father’s medical history, such as information about hereditary diseases, could be important for a child’s overall health maintenance.

Fraternal twins are formed when two separate eggs are fertilized by two sperms. If a woman has contact with different partners within her fertile time period and has multiple ovulations, it is possible for her to have fraternal twins or even triplets with different fathers. This phenomenon has been dubbed in medical literature as heteropaternal superfecundation.

“There is a small time window when eggs are able to be fertilized,” says Dr. Baird. Sperm cells can live inside a woman’s body for 4-5 days. Once ovulation occurs, the egg remains viable for 12-48 hours before it begins to disintegrate. Thus, the fertile period can span 5-7 days.

In her article Multiple Births, Dr. Terence Zach of Creighton University states that the average birth rate of fraternal twinsin the United States is about 8 per 1000 births (identical twins are 4 per 1000 births), although the rate varies by race.

The rate of fraternal twinning and other multiple births has been increasing since the 1970s, with the advent of assisted fertility methods, such as in vitro fertilization (IVF). DDC has had a paternity test case in which the donated sperm for the IVF proved to be a mixture from two males, according to laboratory staff.

“The frequency of twinning is quite low, and so such cases [of twins with different fathers] are even rarer,” says Dr. Baird. “Previous DNA testing methods, based on blood antigens, were able to detect some of these cases, but DNA testing is much more powerful and now we can begin to get more accurate statistics. More accurate paternity testing might prove it to be a long-standing but little known phenomenon.”

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About DDC
DNA Diagnostics Center (DDC) is the world’s largest provider of private paternity tests. Since 1995, DDC has performed hundreds of thousands of genetic tests for clients in all 50 U.S. states and around the world. DDC offers comprehensive DNA testing services in several specialty areas: family relationship testing, forensics, and veterinary DNA testing. As the leading force in the private DNA testing industry, DDC was the first to adopt robotics technology in its laboratoryprocesses for stringent and efficient handling of DNA samples. DDC’s unique Dual Process™ and extended DDC Plex™ panel ensures results of unmatched quality and reliability.
DDC’s quality DNA testing services are nationally and internationally recognized through a number of accreditations from professional organizations such as the American Association of Blood Banks (AABB), ASCLD/LAB-International, theCollege of American Pathologists (CAP), and the Forensic Quality Services (FQS-I, ISO/IEC-17025).