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Does tobacco exposure delay conception?

Institution: Sequoia Foundation
Investigator(s): Michelle Pearl, Ph.D.
Award Cycle: 2003 (Cycle 12) Grant #: 12RT-0202 Award: $447,845
Subject Area: Epidemiology
Award Type: Research Project Awards

Initial Award Abstract
This three-year study addresses the relationship between tobacco exposure in women and delayed time-to pregnancy. Several studies have suggested that smoking by women or their partners can affect fertility and delay conception. But we do not know whether women exposed to passive smoke have reduced fertility or conception delay. Previous studies may have underestimated smoking effects because they did not take passive exposure into account among non-smokers, and because they relied on women's self-reports of smoking. This study of time-to-pregnancy is the first to use a biochemical measure of tobacco exposure capable of detecting passive exposure levels. Data and specimens were collected as part of a previous TRDRP-funded study (#8RT-0115). Women obtaining pregnancy tests were surveyed to determine use of birth control and duration of unprotected intercourse, and consented to storage and testing of leftover urine from the pregnancy test. We will analyze selected specimens for cotinine, a metabolite of nicotine, and model the relationship to time-to-pregnancy. The unique study population permits the creation of multiple study samples to examine potential bias affecting pregnancy-based time-to-pregnancy studies.

In the first year, we have made progress on several fronts including hiring of study personnel, preparation of analytic datasets, preliminary analysis, and creation of study samples. We used probabilistic matching software to link survey forms to live birth certificates and identify women with multiple stored urine specimens. We have created three study groups for analysis: Women at-risk for pregnancy, women with positive pregnancy tests, and women delivering live births who have also completed a hospital survey. Estimates of time-to-pregnancy have been compared across the three study groups of interest by demographic characteristics. Through linkage to self-reported smoking information on completed hospital surveys, we have documented an increase in time-to-pregnancy among smokers relative to non-smokers. By the end of Year 1, we will have completed the sampling and shipping of 1,500 urine specimens for cotinine analysis by the Centers for Disease Control, Tobacco Exposure Biomarkers Laboratory.

In Years 2 and 3, specimens will be analyzed for cotinine and dose-response models will be developed. The results will provide the best assessment to date of active and passive tobacco exposure effects on delayed conception. A positive finding could give couples added incentive to quit smoking or to avoid passive exposure to cigarette smoke, and potentially influence policies directed toward protecting adults from second-hand smoke.