Demographic, behavioral, and reproductive history differences by maternal working status before and during pregnancy: implications for reproductive studies.
Studies of occupational exposures among reproductive-aged women must address biases that could be caused by self-selection to employment. Data from controls in the National Birth Defects Prevention Study with births from 1997-2007 were used, representing a random sample of live births unaffected by birth defects. We compared personal and household characteristics of women who held any job during the 3 months prior to conception through the end of pregnancy (n = 5978, 71.7%) to those of women who did not hold any job in this period (n = 2365, 28.3%). Patterns of maternal work were also evaluated, including: frequency of part-time, full-time, and long work hours; job change; and job cessation. Most women who did not work during this period self-identified as homemakers/parents (80.4%) or students (14.1%); few reported being disabled (1.2%) or between jobs/unemployed (3.5%). Maternal age, parental race, parental nativity, parental education, and household income differed between families of working and nonworking women. Non-working women were more likely to be multiparous compared to working women (73.8% vs. 54.4%). Working women were more likely to have planned their index pregnancy and have used fertility drugs or treatments to conceive, however they were also more likely to report pregnancy risk behaviors including not using a folic acid supplement during the periconceptional period, smoking, drinking alcohol, and paternal (but not maternal) use of illicit drugs. These patterns could introduce bias in studies of occupational exposures in relation to reproductive outcomes that are not restricted to workers only.
Reproduction; Reproductive-system; Women; Pregnancy; Demographic-characteristics; Behavior; Behavior-patterns; Epidemiology; Occupational-exposure; Age-groups; Job-analysis; Household-workers; Workers; Risk-factors; Drugs; Alcoholic-beverages; Cigarette-smoking; Smoking; Fertility; Vitamins; Education; Drug-abuse