Caffeine and the Risk of Miscarriage
Pregnant women can drink a couple of cups of coffee per day without raising the danger of a miscarriage, but six or more cups can double the risk, a study found.
Pregnant women generally are urged to limit their caffeine intake, though studies on this subject have been unclear. Some have found harm in a cup or two a day. Others found the higher miscarriage risk only in women who suffered morning sickness, and still others found no increased risk.
The study, conducted by doctors from the institute and the University of Utah, was published in today's New England Journal of Medicine. The researchers examined stored blood samples that were taken from thousands of pregnant women at 12 sites from 1959 through 1966. That period was about when U.S. coffee consumption peaked.
The researchers measured blood levels of paraxanthine, the primary substance produced when the liver breaks down caffeine. Paraxanthine stays in the blood at more consistent levels than caffeine, so the scientists considered it a good measure of daily caffeine consumption. Besides coffee, tea, soft drinks and chocolate contain caffeine.
The study found the average paraxanthine level was about 30 percent higher in the 487 women who had miscarriages than it was in the 2,087 women who gave birth.
Based on their study and others, the researchers concluded that one to two cups of coffee a day is safe. But the women whose blood had paraxanthine levels corresponding to at least six cups of coffee were 1.9 times more likely than those with very low amounts to have a miscarriage.
Kidney Transplant Trends
Kidney failure patients getting dialysis at for-profit centers are less likely to get on a transplant waiting list and more likely to die than those at not-for-profit institutions, researchers found.
The researchers mainly blame understaffing. But the Johns Hopkins School of Medicine study also raises the possibility that profit-making centers may sometimes be reluctant to arrange kidney transplants because they do not want to lose their patients' dialysis business.
In a second study, Harvard Medical School researchers tried to explain the well-documented racial gap when it comes to kidney transplants. They speculated that prejudice and a breakdown in communication between white doctors and black patients may help explain why whites are nearly twice as likely to get a transplant or get on a waiting list.
Those findings prompted the federal agency that administers Medicare to announce yesterday that it will strengthen enforcement of Medicare rules requiring that all kidney failure patients be evaluated for transplants and informed of their options.
Both studies were published in today's New England Journal of Medicine.
Kidneys filter out toxic substances and excess fluid, so if disease, injury or infection ruins them, survival depends on a transplant or three-times-a-week dialysis. During the several-hour, often-tiring procedure, a machine pumps blood through tubes and filters, then back into the body. About 240,000 Americans undergo dialysis. For most, a transplant can mean a longer, stronger life.