Unique influences of pregnancy and anticipated parenting on cigarette smoking: results and implications of a within-person, between-pregnancy study.

Not all pregnant individuals want to become parents and "parenting intention" can also vary within individuals during different pregnancies. Nevertheless, the potential impact of parenting intention on health-related behavior during pregnancy has been heavily underexplored. In this study, we employed a within-person between pregnancy design to estimate the effect of parenting-specific influences on smoking, separate from pregnancy-specific and individual-level influences. We quantified within-mother differences in smoking during pregnancies of infants they reared (n = 84) versus pregnancies of infants they placed for adoption at birth (n = 65) using multivariate mixed-effects Poisson regression models. Mean cigarettes/day declined as the pregnancy progressed regardless of whether infants were reared or placed. However, participants smoked fewer cigarettes/day during reared pregnancies. Relative to "adopted" pregnancies, smoking during "reared" pregnancies was lower by 24%, 41%, and 54% in first (95% CI 0.64-0.90; p = 0.001), second (95% CI 0.48-0.72; p < 0.001), and third trimesters (95% CI 0.36-0.59; p < 0.001), respectively, independent of between-pregnancy differences in maternal age, fetal sex, parity, and pregnancy complications. Female sex and nulliparity were protective. Parenting intention was associated with a protective effect on pregnancy smoking independent of pregnancy-specific influences and individual characteristics. Failure to consider the impact of parenting intention on health-related behavior during pregnancy could perpetuate an unrealistic expectation to "do what's best for the baby" and stigmatize women with unintended or unwanted pregnancies.