I am pregnant with twins and need to know if my babies can be one day older than the other? Can I have one baby by one dad and the other by another dad?

Not only is it possible for fraternal twins to have different fathers, it’s on the medical record books. This official medical term for this phenomenon is heteropaternal superfecundation.

The classic case was recorded in 1810 by John Archer, the first doctor to receive a medical degree in the U.S. According to Dr. Archer, a white woman who had sex with a black man and a white man within a short time of each other subsequently gave birth to twins—one white, one mulatto. Other cases have been reported since. And you thought this only happened with puppies?

Sperm cells can live inside a woman’s body for four to five days. Once ovulation occurs, the egg remains viable for another 12 to 48 hours before it begins to disintegrate; thus, the fertile period can span five to seven days.

Dr. Lawrence B. Werlin, founder and director of the Coastal Fertility Medical Center in Irvine, Calif., explains, “If the twins are fraternal, where two eggs (ova) are fertilized by two sperm and produce two genetically unique children, then one baby could be slightly older than the other. In addition, if a woman ovulates, releases two eggs and has intercourse with two different men, the eggs could be fertilized by both, resulting in fraternal twins with distinctive fathers.”

Historically, superfecundation has been difficult to prove, due to the crudeness of the blood-type testing methods. However, in 1978, Dr. Paul Terasaki of the UCLA School of Medicine reported in the New England Journal of Medicine that he and his colleagues had conclusively established a case of superfecundation using a sophisticated procedure called tissue HLA (or human leukocyte antigen) testing. Potential paternity-suit litigants, take note: This technique can also be applied to more conventional cases.

(daqui)