Accuracy of self-reported smoking status in first trimester aneuploidy screening.

OBJECTIVES: To review the accuracy of self-reporting of smoking status in our first trimester screening population and to assess the levels of pregnancy-associated plasma protein-A (PAPP-A) and free-β human chorionic gonadotropin (free-hCGβ) in women who were classified for smoking status by serum cotinine concentrations and self-reporting.
METHODS: Cotinine concentration was determined in the stored serum 696 self-reported smokers and 442 self-reported non-smokers. PAPP-A and free-hCGβ multiples of the medians (MoMs) determined at screening were reverted to uncorrected for self-reported smoking status.
RESULTS: A total of 21.7% of those self-reporting as non-smokers had increased serum cotinine concentrations (using a cut-off of 13.7 ng/mL), indicating a positive smoking status. This under-reporting meant that serum PAPP-A and free-hCGβ MoMs were greater reduced in smokers classified by cotinine levels (17.2% and 9.7%) than in those classified by self-reporting (14.6% and 2.8%). Women who were classified as smokers at conception but had stopped at some time afterwards did not have significantly reduced marker MoMs to non-smokers.
CONCLUSIONS: Self-reporting results in under-representation of smoking in our population, resulting in a significant bias and inflated screen-positive rates.