Nicotine & Tobacco Research, Volume 11, Number 10 (October 2009) 1166–1174
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Received February 22 , 2009 ; accepted May 15 , 2009
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interview-based recall of pregnancy smoking may be relatively
accurate, although optimal measurement should combine retro-
spective and prospective self-report and biological assays, as
each provide unique information and sources of error.
Epidemiological studies of the impact of maternal smoking in
pregnancy on outcomes in offspring frequently rely on maternal
retrospective self-report of smoking, sometimes soon after the
pregnancy, sometimes many years later. It is often assumed that
such retrospective reports are rife with recall error and bias. Yet,
only a few studies have empirically examined this question in
relation to prenatal smoking ( Githens, Glass, Sloan, & Entman,
1993 ; Heath et al., 2003 ; Tomeo et al., 1999 ; Yawn, Suman, &
Jacobsen, 1998 ). All report high levels of agreement between
retrospective and prospective measures. However, limitations
of measurement in these studies are problematic because none
examined recall of smoking in a way that captures patterns of
smoking across pregnancy. Among the few studies that have ex-
amined smoking, all used dichotomous measures of smoked
versus not. Further, we are not aware of studies that have exam-
ined this question in relation to timing or intensity of smoking,
the correspondence of recall to biological assays of maternal
smoking, or factors that predict poor recall.
Measurement error that contributes to misclassifi cation of
smoking status may hamper detection of subtle or long-term
effects of maternal smoking during pregnancy. For example, if a
woman stopped smoking as soon as she learned she was preg-
nant, she may retrospectively report being a nonsmoker during
pregnancy, truthfully from her own long-term perspective. She
would be classifi ed in most studies as a nonsmoker or quitter;
Introduction : Retrospective recall of smoking during pregnan-
cy is assumed to be substantially biased, but this has rarely been
Methods : We examined the validity of an interview-based ret-
rospective recall more than a decade after pregnancy, in a cohort
with repeated, multimethod characterization of pregnancy
smoking ( N = 245). Retrospective smoking patterns were exam-
ined in relation to prospective reported and biological estimates
of overall and trimester-specifi c smoking status and intensity.
We also compared characteristics of women whose smoking
status was misclassifi ed by either prospective or retrospective
measures with women whose status was congruent for non-
smoking across timepoints.
Results : In general, sensitivity and specifi city of recalled smok-
ing were excellent relative to both prospective self-reported and
cotinine-validated smoking status and trimester-specifi c inten-
sity. However, measures were less congruent for amount smoked
for women who recalled being heavy smokers. Further, retro-
spective measures captured some smokers not identifi ed pro-
spectively due to smoking that occurred prior to assessments.
Women who would have been misclassifi ed as nonsmokers
based on either prospective or retrospective assessment differed
signifi cantly from congruently classifi ed nonsmokers in a num-
ber of maternal, family, and neighborhood, but not child behav-
Discussion : When epidemiological studies of the impact of
smoking in pregnancy use retrospective methods, misclassifi ca-
tion may not be a signifi cant problem if prenatal smoking is as-
sessed in terms of the pattern across pregnancy. This type of
Women who remember, women who do
not: A methodological study of maternal
recall of smoking in pregnancy
Kate E. Pickett , Kristen Kasza , Gretchen Biesecker , Rosalind J. Wright , & Lauren S. Wakschlag
Kate E. Pickett, Ph.D., Department of Health Sciences and
Hull-York Medical School, University of York, UK
Kristen Kasza, M.S., Department of Health Studies, University of
Gretchen Biesecker, Ph.D., Institute for Juvenile Research,
Department of Psychiatry, University of Illinois, Chicago
Rosalind J. Wright, M.D., M.P.H., Channing Laboratory, Depart-
ment of Medicine, Brigham Women’s Hospital/Harvard Medical
School, and Department of Environmental Health, Harvard
School of Public Health, Boston, MA
Lauren S. Wakschlag, Ph.D., Institute for Juvenile Research,
Department of Psychiatry, University of Illinois, Chicago
Kate E. Pickett, Ph.D., Department of Health Sciences and Hull-York
Medical School, University of York, Seebohm Rowntree Building,
Area 3, Heslington, York YO10 5DD, UK. Telephone:
+44-0-1904-321377; Fax: +44-0-1904-321388; E-mail: kp6@
Nicotine & Tobacco Research, Volume 11, Number 10 (October 2009)
yet her fetus would be at risk for any adverse outcomes associ-
ated with fi rst-trimester exposure.
Smoking in pregnancy is a complex behavior that fl uctuates
over the course of pregnancy ( Pickett, Rathouz, Kasza, Wak-
schlag, & Wright, 2005 ; Pickett, Wakschlag, Dai, & Leventhal,
2003 ). Although much emphasis has been placed on nondisclo-
sure as a source of error, the extent to which mothers truthfully
report whether or not they smoke is only one infl uence on the
accuracy of measurement — others include the timing of mea-
surement, comprehensiveness of assessment, and individual dif-
ferences in smoking topography and metabolism. Retrospective
interviews that query smoking across the course of pregnancy
using methods designed to capture the manner in which moth-
ers structure their behavior can substantially improve the reli-
ability of reporting ( Brigham et al., 2008 ). Similarly, biological
assays are useful for obtaining a prospective direct measure of
smoking but refl ect approximately only the previous 24 hr.
In addition to the complex nature of smoking behavior and
its impact on the validity of recall, it is likely that errors in ma-
ternal recall do not occur randomly, but little is known of the
maternal and family characteristics that infl uence them. Studies
have shown that recall of past events other than smoking may be
infl uenced by maternal characteristics such as mood, personality,
and mental health problems ( Jaffee & Price, 2007 ). For ex-
ample, maternal antisocial tendencies may be associated with
nondisclosure or underreporting because lying is a characteris-
tic of antisocial behavior, or alternatively with more accurate
reporting because of a lack of concern with conforming to social
mores. Maternal depression has also been associated with sys-
tematic reporting errors. Maternal socioeconomic status may
also infl uence validity of reporting due to varying social norms
around smoking in different socioeconomic and social class
contexts ( Pickett, Wakschlag, Rathouz, Leventhal, & Abrams,
2002 ). Having a child with a mental health problem may also
introduce bias in recall ( Jaffee & Price, 2007 ).
The direction and magnitude of bias caused by the misclas-
sifi cation of smoking during pregnancy will depend on the
magnitude of the true effect of exposure, as well as the degree of
misclassifi cation. Under most plausible scenarios, however, mis-
classifi cation is likely to lead to an underestimate of the true risk.
Previously reported simulations of the effects of misclassifying
smoking during pregnancy in epidemiological studies found
that the underestimation of the relative risk for smoking on
hypothesized adverse outcomes ranged from <10% to 55%
under varying misclassifi cation scenarios ( Pickett et al., 2003 ).
In this study, we address gaps in research on the validity and
reliability of maternal recall of smoking within a unique cohort
with repeated prospective measurements of smoking that in-
clude both self-report and biological assays, along with retro-
spective recall of pregnancy smoking patterns and rich data on
maternal and family characteristics and social context. We link
these to address the following research questions:
1. What is the congruence between maternal retrospective report of
prenatal smoking and prospective measurement? Does this vary
by measurement method, timing, and intensity of smoking?
2. Are maternal, family, neighborhood, and child behavior
characteristics related to the misclassifi cation of smoking by
prospective and retrospective reports?
Data and study sample
For these analyses, we used data collected during a follow-up
study of a prospective cohort of pregnant women and infants
who were enrolled in 1986 – 1992. The study was originally
established as the Maternal – Infant Smoking Study of East Boston
to compare the relative effects of in utero and early-life exposure
to cigarette smoke on infant lung function ( Hanrahan et al.,
1992 ; Tager, Ngo, & Hanrahan, 1995 ). The follow-up was con-
ducted as the East Boston Family Study (EBFS) as the offspring
entered adolescence, with a primary aim of investigating the
long-term impact of smoking in pregnancy on offspring behavior
( Wakschlag et al., 2009 ). Follow-up data presented here are
drawn from Wave 1 of EBFS. In this paper, pregnancies are the
unit of analysis, and eligibility is restricted to the 245 pregnancies
where the biological mother was interviewed and smoking
information was available in both the original study and the
follow-up study. (Detailed descriptions of the sampling and
eligibility criteria are available in Supplementary Materials .)
Prospective measurement of smoking
and cotinine levels during pregnancy
Women were recruited at the fi rst prenatal visit; the timing of
this varied from 10 to 27 weeks gestation, with 21% recruited in
the fi rst trimester. They were asked at baseline about their past
and current smoking status. At each subsequent prenatal visit
(modal number of visits = 7, range 1 – 12), women reported cur-
rent smoking habits, including the number of cigarettes being
smoked per day. A urine sample was collected and analyzed for
measurement of cotinine by radioimmunoassay at each of these
visits. Urine cotinine values were corrected for urine concentra-
tion and expressed as nanogram per milliliter of urinary creati-
nine. We have reported previously on the complexity of
concordance between prospective self-report and cotinine mea-
sures in this sample ( Pickett et al., 2005 ). In brief, the sensitivity
and specificity of prospective self-report compared with
cotinine-indicated smoking were 88.4% and 99.0%, respectively.
Retrospective measurement of smoking
In the follow-up study, women were asked to recall their smok-
ing behavior during pregnancy. The mean duration of recall was
14.5 years ( SD = 1.7 years); study offspring were aged from 11 to
18 years. Women were asked how many cigarettes per day they
smoked before they knew they were pregnant, in the fi rst trimes-
ter after they knew they were pregnant, and in the second and
third trimesters. They were also asked about current smoking
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( Skinner, 1982 ); problematic alcohol use, assessed as a score >4
on a modifi ed 51-item version of the Michigan Alcoholism
Screening Test ( Selzer, 1971 ); and antisocial behavior, assessed
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