42. Milk Drinkers More Likely To Have Twins

Women who consume milk and other dairy products have twins more than twice as often as do vegan moms, according to Long Island Jewish Medical Center obstetrician Gary Steinman. The finding may help explain the strange 60 percent surge in the rate of twin births in the United States between 1977 and 2002.

The study, published in May in the Journal of Reproductive Medicine, compared the frequency of twins in the general population with that in the obstetrical histories of 1,042 vegan mothers. Steinman suspects that the disparity may be due to a protein in milk called insulin-like growth factor (IGF), which is associated with multiple ovulation. Vegans have lower blood concentrations of IGF than women who consume dairy regularly. Although IGF is present in other animal products, including meat, it seems to survive digestion only when in milk.

Of course, reproductive technologies like in vitro fertilization increase the twinning rate, as does the trend of delaying childbirth, but Steinman argues that dietary factors also play a role. In 1993 the FDA approved the use of recombinant bovine growth hormone in cows for the purpose of increasing milk production; milk from hormone-treated animals is especially rich in IGF. Between 1992 and 2001, the twinning rate in the United States increased twice as much as it did in the United Kingdom, where the hormone is banned. "We're doing something different," Steinman says, "and the only difference I can find is this growth hormone."

Jennifer Barone

47. Cesareans Boost Death Risk for Baby

A study of nearly 6 million low-risk births has found that the neonatal mortality rate for delivery by cesarean section is nearly three times the rate for vaginal delivery: 1.77 deaths per 1,000 live births via cesarean, as opposed to 0.62 deaths per 1,000 for vaginal delivery. By limiting their survey to full-term pregnancies with no complications, Marian MacDorman, of the Centers for Disease Control and Prevention, and colleagues eliminated the influence of medically necessary cesareans. While it's not clear why vaginal birth is safer for infants, previous studies suggest that hormones released during labor may help prepare babies to breathe outside the womb. In 2004, C-sections accounted for nearly 30 percent of American births.

Jennifer Barone

60. Polio's Return Traced to Lapses in India

In May a 39-year-old man in Namibia tested positive for poliovirus, marking the country's first case in 10 years. Since then, the outbreak there has reached 20 confirmed cases. This year 10 other formerly polio-free countries are once again battling the disease. Genetic sequencing has traced cases in five of the countries, including Namibia, to a polio strain in India, where the virus remains endemic. As of October 2006, a total of 358 cases have occurred in the poor, densely populated north Indian state of Uttar Pradesh alone, up from 29 in 2005. The World Health Organization has taken India to task, saying its outbreak is endangering efforts worldwide to keep the disease at bay. To protect a high-risk community from polio, at least 95 percent of the children must be vaccinated; but in late 2005 and early 2006 the vaccination rates in Uttar Pradesh dipped to between 85 and 90 percent. The Indian government, vowing to eliminate polio by 2007, has discussed a pilot project using an injectable vaccine in addition to oral drops. The injectable vaccine is thought to offer better protection against polio infection in children with diarrhea, which is common in the area.

Apoorva Mandavilli