Self-reported cigarette smoking status imprecisely quantifies exposure in pregnancy

Carolina C Venditti,Graeme N Smith

doi:10.4236/ojog.2012.21010

Abstract

Objective: We sought to determine the validity of self-reported smoking activity versus two quantitative measurements of tobacco exposure in pregnancy. We hypothesized that pregnant women would under-report their daily smoking amounts, due to the negative social stigmas associated with such a behavior. Methods: Cigarette-smoking and non-smoking pregnant women were recruited as part of a larger research study. Pregnant women with a singleton baby (>24 weeks) were recruited at a clinical appointment or prior to an elective caesarian section. Self-reported smoking status, including time since last cigarette, was recorded. End-tidal breath carbon monoxide (ETCO) levels and urine cotinine levels were measured and compared. Results: Both normotensive non-smoking (NTN) (n = 44) and normotensive smoking (NTS) (n = 24) pregnant women were recruited. A strong correlation was found between ETCO levels and urine cotinine measurements (r = 0.6566, p 0.05). Conclusion: Self-reported smoking status accurately identifies women who smoke in pregnancy, but not their level of tobacco exposure. Urine cotinine or ETCO are much better quantitative measurements of nicotine and carbon monoxide, respectively, and should be measured for a more precise indicator of smoking activity. These devices will allow for better counseling and monitoring of women who are trying to quit smoking and/or who enter into smoking cessation programs.

Highlights

In Canada 17% of women smoked during their pregnan-cies from 1995-2001 [1], despite the many adverse consequences, such as premature birth, low birth weight and cognitive abnormalities, that have been linked with maternal smoking [2]
Many clinicians rely on patient reporting to estimate tobacco exposure [3,4,5,6], these reports are subject to error due to the possibility of false reporting [7,8,9], second-hand exposure, an accelerated metabolism of cigarette by-products in pregnancy, and inconsistent smoking habits [10]
The problem lies in the amount of cigarette smoking, and tobacco exposure, that women disclose to their physician

Summary

Introduction

In Canada 17% of women smoked during their pregnan-cies from 1995-2001 [1], despite the many adverse consequences, such as premature birth, low birth weight and cognitive abnormalities, that have been linked with maternal smoking [2]. Pregnancy seems to be the perfect opportunity for clinicians to offer anti-smoking advice, as women are frequently returning for appointments, and can be monitored regularly. Many clinicians rely on patient reporting to estimate tobacco exposure [3,4,5,6], these reports are subject to error due to the possibility of false reporting [7,8,9], second-hand exposure, an accelerated metabolism of cigarette by-products in pregnancy, and inconsistent smoking habits [10]. It can be extremely difficult to counsel patients on their smoking habits due to under-reporting or nondisclosure. McClure reported that the use of a biochemical method to validate smoking habits can more effectively motivate women to stop smoking in pregnancy [11]. Uses of biochemical markers of cigarette smoke absorption, such as the nicotine metabolite cotinine and exhaled end-tidal carbon monoxide (ETCO) levels have been suggested as more accurate measures than questionnaires, due to the objectivity of their measurements [7]

Methods

Results

Discussion

Conclusion