According to a study conducted in Guatemala, women who experience stress in the first weeks of the pregnancy have an increased risk for a miscarriage. Previous studies on this topic failed to provide valuable results because they looked at women at least six weeks from their menstrual period and miscarriages usually occur in the first three weeks of the pregnancy. The study looked at 61 women over a one year period, collecting urine samples three times a day. From these women, only 22 managed to get pregnant. Out of the 22 pregnancies which presented a high level of stress hormone in the urine samples, 12 resulted in a miscarriage. Women with a high level of cortisol, a hormone linked to stress, are 2.7 times more likely to suffer a miscarriage. Pablo Nepomnaschy, from the National Institute of Environmental Health Sciences of the National Institutes of Health in Research Triangle Park, suggested that a woman should try to provide herself with a good environment, to minimize the stress level. Dr. Mary Stephenson, obstetrician-gynecologist at the University of Chicago, said about the other studies which looked at the link between cortisol and pregnancy: "The results have been conflicting. There are some studies in animals that suggest that stress increased the risk of miscarriage. And doctors have long suspected that stress does the same in people." About 15% of pregnancies occur with a miscarriage", said Stephenson, but "when you count the ones that occur before six weeks, up to half of pregnancies end in miscarriage." As for a recommendation from behalf of the doctor, she advices future mothers: "I recommend that before they get pregnant, they take a serious look at their lifestyle."