Pregnant women exposed to armed conflict have a higher risk than others of giving birth to babies who are under weight, U.S. researchers say. Hani Mansour and Daniel Rees of the University of Colorado Denver and Daniel Rees said the Second Intifada, which began in September 2000, claimed more than 4,000 Palestinians by 2005. Mansour and Rees used data from the Palestinian Demographic and Health Survey, collected by the Palestinian Central Bureau of Statistics approximately four years after the start of the uprising. The data were matched with data on Palestinian fatalities in the West Bank collected by B'Tselem, an Israeli human rights organization. The researchers examined a sample of 1,224 births to women living in the West Bank. Conflict exposure in utero was measured by the number of Palestinians killed by Israeli security forces in the district where the mother lived. The authors controlled for a variety of potentially confounding variables -- including education of the mother and father, mother's age when she gave birth, father's occupation, birth order, gender of the baby, number of prenatal care visits, whether a curfew was in place and self-reported anemia. Because they controlled for anemia, the professors said that psychological stress, as opposed to malnutrition, is the likely mechanism behind low birth weight. "We find that an additional conflict-related fatality nine to six months before birth is associated with an increase in the probability of having a low-birth weight child," Mansour said in a statement. "Psychological stress is a plausible explanation for this relationship, although we cannot rule out malnutrition." The findings were published in the Journal of Development Economics.