Of thousands of mothers who participated in a 30-year study, the ones who had delivered children outside of marriage reported being less healthy when they reached their 40s than the ones who had postponed motherhood until after marriage. And marriage, when it occurred after motherhood, did not appear to remedy the women\'s health problems, said study researcher Kristi Williams, an associate professor of sociology at Ohio State University. The findings suggest public health campaigns to promote marriage, which were started by the government in 1996 and aimed at single, low-income mothers, may not improve these women\'s health as once hoped, the researchers said. Because many more women have out-of-wedlock children today than several decades ago, the researchers predicted an increasing public health problem as these women enter their midlife. About 40 percent of newborns in the United States come from single moms, compared with 10 percent in 1960, the researchers said. Williams and her colleagues analyzed survey responses from close to 4,000 women who were ages 14 to 22 when the study began in 1979. The women were interviewed every year until 1994, and then every two years afterward until 2008. Women who had their first child out of wedlock reported lower levels of health at age 40 than did those who were married when they had their first child. The results held even after the researchers took into account factors that could influence the mother\'s health, including education level and health conditions that existed before 1979. Getting married later on did not tend to ameliorate the single mother\'s poor health unless she married the biological father, remained married to him, and was white or Hispanic. There was no beneficial effect of later marriage for black mothers, the researchers said. The study did not determine why single mothers had poorer health, but the researchers speculated it may be due to the stress and financial strain that often accompany single parenthood. Both of these factors are implicated in a wide range of health problems, Williams said. It\'s important to note a bad relationship or bad marriage also can be deleterious to one\'s health. For instance, a 2009 study found women who have more conflict in their relationships have a higher risk for health conditions such as high blood pressure and high blood sugar. The researchers noted the study was relatively small and was based on self-reports of health. The study suggested policymakers should look for other ways to help single mothers improve their health, Williams said, such as providing access to job training, child care assistance and health insurance. Other experts agreed that the increase in the number of single mothers could lead to public health problems down the road. One suggested that the lack of financial support was the main driver of poor health. Women who have children out of wedlock today may have different levels of income and family support  than the single moms of  decades ago, said William Avison, a sociologist at the University of Western Ontario in Canada, who was not involved with the study. The health effects seen in this study were probably largely a result of the single mothers\' economic disadvantage, Avison said. If a large percentage of single mothers today had the family and financial support they needed to raise a child, then they might face fewer health problems. \"In the long run, it\'s still a case of the socioeconomic disparities that produce all sorts of negative outcomes for people,\" Avison said. The new study will be published in the June issue of the journal American Sociological Review.