The odds of having two sets of twins at once is about 1 in 70 million, said Dr. Alan Penzias, associate professor of obstetrics, gynecology and reproductive biology at Harvard Medical School.

CNN: Texas woman has 2 sets of identical twins

Professor Malcolm Parker, and Dr Jan Brosens from the Institute of Reproductive and Developmental Biology at Imperial College, London, wrote in an accompanying commentary that it was still difficult to prove a link between dioxins and human disease.

BBC: Clues to dioxin danger

"For men, the problem was with their genitals, and that was a lot easier to fix than fixing a problem in the brain, " said Sheryl Kingsberg, a clinical psychologist and professor in both the departments of reproductive biology and psychiatry at the Case Western Reserve University School of Medicine.

CNN: When a woman doesn't want sex

As a veterinarian, Travis said his interest in wildlife conservation got him into reproductive biology and research aimed at fighting infertility and exploring birth control methods.

MSN: Scientists look to sperm to power nanobots

Of more than 40, 000 vertebrate species on the planet, the reproductive biology of fewer than 100 (among them humans and most domestic livestock) are known in any detail.

ECONOMIST: Endangered species