ISLAMABAD (Online)- Women who gain more than 40 pounds (18 kg) during pregnancy have nearly twice the risk of delivering a heavy baby as those who gain less, U.S. researchers said on Friday. The study of more than 40,000 U.S. women and their babies found as many as one in five women gains too much weight during pregnancy, doubling the chances her baby will weigh 9 pounds (4 kg) or more. And they found women who gain more than 40 pounds during pregnancy are more likely to have a heavy baby even if they do not have gestational diabetes, a short-term form of diabetes linked with pregnancy that is known to increase the risk of having a big baby. "Because there are so many women who are gaining more than 40 pounds during pregnancy, it's an important health message for most women to avoid excessive weight during pregnancy," Dr. Teresa Hillier of Kaiser Permanente Center for Health Research in Portland, Oregon, whose study appears in the journal Obstetrics & Gynecology, said in a telephone interview. Hillier said gaining extra weight during pregnancy increases the risk for having heavy babies, and studies suggest these babies are programed to become overweight or obese later in life. According to the American College of Obstetricians and Gynecologists, babies who weigh more than 9 pounds at birth are considered heavy. A large baby can pose risks for a difficult delivery " increasing the chances of vaginal tearing, bleeding, and Caesarian-sections for the mother and the risk of stuck shoulders and broken collar bones for the baby. In the study, Hillier and colleagues examined the medical records of 41,540 women who gave birth in Washington, Oregon and Hawaii from 1995-2003. All had been tested for gestational diabetes and 5.4 percent were treated for it with a program of diet, exercise and insulin, if needed, to control blood sugar. Overall, 20 percent of the women in the study who gained more than 40 pounds " the upper limit of pregnancy weight gain recommendations in the United States " gave birth to heavy babies. Fewer than 12 percent of women in the study with normal weight gain delivered heavy babies, she said. The group at greatest risk were those who gained more than 40 pounds and had gestational diabetes. Nearly 30 percent of these women had heavy babies, compared with 13.5 percent of women with gestational diabetes who had normal weight gains during pregnancy. The researchers said the findings suggest all women should avoid excessive weight gain during pregnancy. And women who are being treated for gestational diabetes should also strive to keep weight gain below 40 pounds. "You can't treat the glucose and ignore the weight gain issue," Hillier said. Weight gain during pregnancy has been rising over the past two decades, and some researchers suspect this may be fueling an epidemic of childhood obesity. Illness, aging may not change end-of-life choices People who say they wouldn't want life-sustaining treatments if they were brain dead tend not to change their minds over time, but the preferences of those who want more aggressive treatment are less stable, a new study of aging doctors suggests. Dr Marsha N. Wittink of the University of Pennsylvania School of Medicine in Philadelphia and her colleagues also found that aging or changes in study participants' mental and physical health had little influence on their treatment preferences. But the doctors who didn't have advance directives were more likely to change their minds. Advance directives are documented instructions on a person's preferences for medical care if they lose the ability to make such choices for themselves. "That suggests to us that there's something very deliberate about going through that process" of creating an advance directive, Wittink told Reuters Health. "What the average person might want to take from this is that the process of sitting down with your family and loved ones and physician is an important one." To gauge the stability of preferences in end-of-life care, the investigators used data from the Johns Hopkins Precursors Study, one of the longest-running studies of aging in the world. It is open to everyone who graduated from the university's School of Medicine from 1948 to 1964, and was designed to examine risk factors for premature heart disease and death. Wittink and her colleagues looked at 1999 and 2003 survey results for 818 of the study's participants, who were asked whether or not they would want 10 different types of life-sustaining treatment if they had suffered permanent brain damage and were no longer able to speak or recognize people. The researchers grouped them into three categories based on the aggressiveness of their treatment preferences. In 1999, 62 percent of the study participants fell into the "least aggressive" category, 26 percent opted for intermediate care, and 12 percent opted for the "most aggressive" care. Three years later, the breakdown was virtually identical, but 60 percent chose the least aggressive care and 14 percent chose the most aggressive. Eighty percent of the physicians who initially chose the least aggressive care made the same choice three years later. But just 41 percent of those who had first said they preferred the most aggressive care still did at the second survey. A person's mental or physical health didn't have much influence on whether or not they changed their preferences. But the doctors who did not have advance directives were twice as likely to change their preferences as those who did. Physicians have a clear understanding of what's involved in life-sustaining treatments such as mechanical ventilation, intravenous fluids, and tube feeding, Wittink noted in an interview, so their end of life preferences may be more stable than those of people in the general population, who have less information on these treatments.