Abstract Most previous studies of preterm birth have
considered risk factors in isolation rather than examining
the collective impact of multiple candidate determinants.
In order to examine the combined impact of a set of
behavioral risk factors on the risk of preterm birth, we
analyzed data collected for the Pregnancy, Infection, and
Nutrition Study on a range of sociodemographic, behavioral,
and related factors. Women who received prenatal
care at selected clinics in central North Carolina and gave
birth in the period 1995–2005 were recruited into a prospective
cohort study, with 4,251 women providing therequired information on risk factors and pregnancy outcome.
A number of demographic and behavioral attributes
were modestly associated with preterm birth, with odds
ratios of 1.3–1.5, including age [35, African-American
ethnicity, height of 63 inches or less, parity 2?, and
delivery at the academic medical center. Despite weak
associations for individual risk factors, changes in a constellation
of behaviors during pregnancy predict substantial
shifts in the risk of preterm birth, suggesting a
reduction from 8 to 3% preterm among those with a lowrisk
baseline profile, and a reduction from 18 to 7% preterm
among those with a high-risk baseline profile. While
inferences are limited by the incomplete range of available
predictors, uncertainty regarding whether observed associations
are causal, and substantial challenges in changing
component behaviors, the possibility of substantial
reduction in risk merits more serious consideration of
whether behavioral interventions could markedly reduce
the risk of preterm birth.