Certain maternal behavioral factors--including receiving prenatal care, low pregnancy-related weight gain and smoking during pregnancy--are significantly associated with low birth weight, according to a 2001 survey of women who gave birth in public hospitals in western Mexico. (1) Social, demographic and economic factors--including age, union status, locality size and working during pregnancy--have an indirect effect on low birth weight through their associations with prenatal care.

To identify factors associated with low birth weight, researchers recruited for a 2001 survey women giving birth at one of eight Ministry of Health public hospitals in two western Mexican states. All women who had delivered a low-birth-weight infant (defined as weighing less than 2,500g) were eligible for the survey; researchers randomly selected a sample of mothers of normal-weight infants to participate. Trained female interviewers asked participants while in the hospital's recovery ward about their social and demographic characteristics and certain behavioral factors (i.e., smoking during pregnancy, prenatal care and pregnancy-related weight gain), and whether they had experienced health problems or hospitalization during pregnancy. Logistic regression analysis was used to determine which factors were associated with low birth weight and with prenatal care.

The sample consisted of 565 women: 257 who had delivered a low-birth-weight infant and 308 whose infant was born at a normal weight. Seventy-two percent of respondents were aged 20-34; 21% were younger and 7% were older. The index birth was the first for about one-third of respondents; approximately...