Exposure to Multiple Risk Factors Linked to Delivery Of Underweight Infants
commonly engage in or are exposed to multiple risk factors during pregnancy, and these risk factors have a cumulative, perhaps synergistic effect on their risk of delivering an infant who is small for gestational age.1 According to an analysis of data from a multistate U.S. survey, between 5% and 57% of women engage in or are exposed to risk factors, such as smoking, inadequate weight gain and various types of stress, during pregnancy. Those who have four or more risk factors are between two and four times as likely to deliver an infant who is small for gestational age as women without exposure to any risk factors.
To understand the association between multiple risk factors during pregnancy and the risk of bearing an underweight baby, researchers analyzed data collected in 1997 by the Pregnancy Risk Assessment Monitoring System, which surveys women with recent deliveries on their behaviors and experiences during pregnancy. Questionnaire responses from 19,331 women in 13 states with survey response rates of 70% or more were examined for the following specific risks: cigarette smoking, alcohol use, inappropriate maternal weight gain, timing of entry into prenatal care, unintentional pregnancy, physical violence, partner-associated stress, emotional stress, traumatic stress and financial stress. Data collected from birth certificates were also used. Researchers estimated gestational age by calculating the time between the date of last menstruation and the date of birth. Infants' birth weights were determined, and a designation of small for gestational age was given to infants in the 10th or lower percentile of birth weight for gestational age by gender.
Of the respondents, 77% were white, 19% were black and 4% categorized themselves as belonging to other races. The majority of women were married, were between 20 and 34 years of age, had a high school education or greater, and had more than one child. Forty-six percent were enrolled in the Special Supplemental Nutrition Program for Women, Infants and Children (WIC), and 39% received prenatal care services that were covered by Medicaid.
Between 31% and 57% of the women surveyed reported that they had gained less than or more than the recommended amount of weight during pregnancy; that they had experienced partner-associated, emotional or financial stress; or that they had not intended to become pregnant. Between 14% and 23% had smoked cigarettes, experienced traumatic stress or entered into prenatal care late or not at all; 5-6% had drunk alcohol or experienced physical violence during pregnancy. Of the total sample, 3% delivered infants who were underweight at birth.
Approximately 10% of all women surveyed were not exposed to any of the risk factors studied. Nineteen percent were exposed to one risk factor, 21% to two, 19% to three, 14% to four, 10% to five and 7% to six or more. Certain demographic factors were linked to increased exposure to multiple risk factors during pregnancy. Black women, women younger than 25, women without a high school education, unmarried women, women with two or more children, and those enrolled in WIC or Medicaid were more likely than others to engage in or be exposed to multiple risk factors during pregnancy.
After controlling for age, race, education, marital status, parity, WIC and Medicaid enrollment, and state of residency using multivariate analysis, the researchers found that women exposed to multiple risks were significantly more likely than women exposed to no risks to deliver an infant who was small for gestational age. Women with four risk factors were twice as likely as those with none to have an infant who was underweight at birth (odds ratio, 2.1). Women with five risk factors and those with six or more were almost four times as likely to have an infant who was small for gestational age as women without any risks or exposure (odds ratios, 3.5-3.8).
Despite the study's limitations, such as recall bias and the assumption that each risk factor is of equal weight, the researchers conclude that women do engage in or are exposed to multiple risks during pregnancy and that "the results indicate a need for care providers to assess an array of risks to devise appropriate and timely intervention strategies." They add, "Early recognition and assessment of not only individual behaviors but also multiple-risk behaviors and exposures are recommended along with strategies for targeting pregnant women in prenatal care and other health care settings to promote healthy pregnancies and better birth outcomes."--J. Rosenberg
1. Ahluwalia IB et al., Multiple lifestyle and psychosocial risks and delivery of small for gestational age infants, Obstetrics & Gynecology, 2001, 97(5):649-656.