LIFE Study Supporting Statement Part B _3_25_08_

Supporting Statement B
Longitudinal Investigation of Fertility and the Environment – NICHD

March 25, 2008

Germaine M. Buck Louis, PhD, MS
Epidemiology Branch
Division of Epidemiology, Statistics & Prevention Research
Eunice Kennedy Shriver National Institute of Child Health & Human Development
Department of Health and Human Services
6100 Executive Blvd., Room 7B03
Rockville, MD 20852
Tel: (301) 496-6155
Fax: (301) 402-2084
email: louisg@mail.nih.gov

Table of Contents
Page
B. COLLECTIONS OF INFORMATION EMPLOYING STATISTICAL METHODS
B.1. Respondent Universe and Sampling Methods .....................................................
Respondent Universe………………………………………………………...
Sampling Methods……………………………………………………………
B.2. Procedures for the Collection of Information ......................................................

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5
8
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B.3. Methods to Maximize Response Rates and Deal with
Nonresponse ........................................................................................................ 12
B.4. Test of Procedures or Methods to be Undertaken................................................ 14
B.5. Individuals Consulted on Statistical Aspects and Individuals
Collecting and/or Analyzing Data ....................................................................... 16
References....................................................................................................................... 18

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LIST OF TABLES

Table 1. Recruitment Strategy and Expected Response Rates by Research Site ......... 9
Table 2. Summary of Estimated Statistical Power by Study Hypothesis ..................... 12
Table 3. Individuals who have Provided Statistical/Methodological Consultation to
the Longitudinal Investigation of Fertility and the Environment.................... 17

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LIST OF ATTACHMENTS

Attachment 1.a. Data Collection Schedule
Attachments 1.b.-o. Data Collection Instruments
1.b. Screening Instrument – Female Version
1.c. Screening Instrument – Male Version
1.d. Female Baseline Questionnaire
1.e. Male Baseline Questionnaire
1.f. Female Time to Pregnancy Journal
1.g. Male Time to Pregnancy Journal
1.h. Pregnancy Journal
1.i. Baseline Saliva Sample Instruction Sheet
1.j

High Fertility Saliva Sample Instruction Sheet

1.k. Semen Specimen Instruction Sheet
1.l.

Fertility Monitor Instruction Sheet

1.m. Pregnancy Test Instruction Sheet
1.n.

Blood Specimen Information Sheet

1.o. Urine Specimen Information Sheet
Attachments 2.a.-c. Brochure, Letter and Informed Consent Forms
2.a.

Example Letter of Introduction

2.b.

Study Brochure

2.c.

Informed Consent Documents (Michigan & Texas Research Sites)

Attachment 3. Institutional Review Board Approvals and National Institute of Health
Reliance Agreement (Michigan & Texas Research Sites and Data Coordinating Center)

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Attachments 4.a.-d. Other Supporting Documentation
4.a. Listing of Testing, Analytes & Metals to be Measured by Matrix and Required
Volume
4.b. Summary of Published Prospective Pregnancy Studies with Preconception
Enrollment
4.c. Summary of Public Comments and Response by the NICHD
4.d. Illustrations of Data Collection Devices

60-day Federal Register Notice (60-Day FRN)
30-Day Federal Register Notice (30-Day FRN)

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B. 1. Respondent Universe and Sampling Methods

Respondent Universe
A prospective cohort study design comprising couples interested in becoming pregnant in
two well-defined geographic areas is underway to capture longitudinal collection of data
on lifestyle factors and menstrual cycle characteristics over the time period in which
couples are attempting pregnancy. This approach permits empirical evaluation of
accession and drop out biases. Couples are being recruited prior to conception (i.e.,
preconception enrollment) to assess a spectrum of sensitive reproductive and
developmental outcomes that can only be ascertained in this manner (e.g., time required
for conception, and early pregnancy loss as measured by human chorionic gonadotropin
hormone (hCG)). This allows us to capture most postimplantation pregnancies and losses
long before clinical recognition (Wilcox et al., 1988) to assess exposures at critical
windows such as before, at or shortly after conception that are capable of disrupting
human development, while at the same time establishing a temporal ordering between
exposure and outcome (Chapin et al., 2004).

Measuring the time required for couples to conceive has the added advantage of
providing a valid estimate of incident infertility or the absence of conception after 12+
months of regular intercourse without the use of contraception, especially given the
absence of incident data in the United States. The National Survey of Family Growth has
done an excellent job measuring the prevalence of impaired fecundity and infertility for
some subgroups of the population and report increasing rates for the more recent U.S.
birth cohorts and subgroups such as women aged 20-24 years and non-whites (Stephen

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and Chandra, 1998). Some authors interpret this to be consistent with an environmental
etiology.

The study cohort has been recruited by two contractors - RTI International and Texas
A&M University System (TAMU) School of Rural Public Health – who have sampled
licensed fish holders or likely anglers as designated by marketing research. In each
geographic site, state fish consumption advisories exist to advise the public about ways to
minimize exposures associated with eating fish
(www.mde.state.md.us/assets/document/fish/advisory_summary.pdf;
www.michigan.gov/documents/FishAdvisory03_67354_7.pdf;
www.tdh.state.tx.us/bfds/ssd/pdf/FishAdvisoryBooklet2004.pdf).

We are targeting anglers as they have been reported to consume more fish than nonanglers, thereby, enhancing the likelihood of a range in exposure for persistent
compounds that have bioaccumulated and magnified with the aquatic ecosystems. The
sampling strategy is purposefully designed to include couples from medically
underserved and/or socioeconomically disadvantaged geographic areas, given concerns
about environmental injustice (i.e., poorer individuals are more likely to reside closer to
environmental hazards than wealthier individuals) (Sexton 1997). The limited body of
evidence to date stems largely from convenient samples of white women from middle
class backgrounds (Axmon et al., 2000; Buck et al. 2004). Based upon existing
prospective pregnancy studies with preconception enrollment, we anticipated that
between of 0.8 to 4.0% of women of reproductive age will be planning pregnancies at

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any point in time (Buck et al., 2004). However, our realized experience to date suggests
that this figure is <1.0%, similar to that reported for two other population based studies
in Denmark and France (Bonde et al., 1998; Slama et al., 2006). Population-based
research involving women of reproductive age in Pittsburgh as directed by Dr. Anne
Sweeney (PI for TAMUS site) reported that 5% of women were planning to become
pregnant (Sweeney et al., 1989) similar to NSFG estimates (Abma et al., 1997).
Recruitment strategies and enrollment targets are rooted in the idea that approximately
120 women of reproductive age will need to be approached to enroll one woman who is
planning to become pregnant. Telephone screening has been used to identify eligible
couples (i.e., women aged 18 to 40 years and men aged 18+ who are planning a
pregnancy).

Sampling Methods
A population-based approach is being attempted to identify and recruit couples planning
pregnancies in three geographic U.S. sites. Each research site has targeted anglers or
individuals with fishing interests of who are of reproductive age and residing near
contaminated water bodies. Most anglers and/or their families consume at least some of
the fish that they catch, placing them at higher risk of exposure to the study chemicals of
interest (Belton et al., 1986), especially minority anglers (West, 1992).

Access to state fish license registries for research purposes varies, as does the type of data
included in those registries. This necessitates flexibility with regard to defining the
target population and recruitment strategy at each site (see Table 1). The Texas site is

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using the Texas Parks and Wildlife Department’s angler database to recruit participants
from ten counties along the Gulf Coast. Access to Michigan’s angler registry is restricted
by law (Michigan Public Act No. 442 of 1976, as amended, 15.243, Section(1)(a); as
such, RTI International recruited study participants by using a commercially available
marketing database (InfoUSA®) to sample from four counties in Michigan. To ensure a
diverse study population, each site has oversampled individuals of a racial or ethnic
minority. Oversampling has been operationalized in a manner consistent with other
government-sponsored projects such as the Current Population Survey and the National
Medical Expenditure Survey (Cohen et al., 1987; Singh et al., 1994). [Please note that
the requested OMB extension for which this application is being submitted requires only
continued recruitment in Texas. The Michigan site has completed recruitment.]

Table 1. Recruitment Strategy and Expected Response Rates by Research Site
Research Site
Target Area
Recruitment
Strategy
Initial Contact
Approach
Size Target
Population
# Couples
Enrolled/ #
Completing
Response

Michigan
4 counties
InfoUSA® identify
people with fishing
interests
Bulk mailing with
telephone follow-up

Texas
10 counties
State fishing license
registry

234,182 individuals

188,601 individuals

104/72

396/317

Actual = 69%

To date, 80%

Bulk mailing with
telephone follow-up

NOTE: The Michigan site has completed all data collection. This extension pertains only to the Texas site.

B. 2. Procedures for the Collection of Information

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The absence of a sampling framework for couples of reproductive age planning
pregnancies complicates the ability to truly define the target population. Fish license
registries in Texas have been merged with InfoUSA® to weight selection by age to
maximize sampling individuals or reproductive age in the event of missing registry data.
RTI statisticians assessed the capture of InfoUSA® households in relation to 2000 U.S.
Census data and finds comparable listing for the four Michigan counties, i.e., 173,347
and 172,522, respectively.

Two competitively chosen research sites were selected for the recruitment of 500 couples
for up to 12 months as they try to conceive to become pregnant (most will become
pregnant within the first three months) and through pregnancy for couples achieving a
clinical pregnancy (a minimum of 400 couples are expected to complete the entire study
protocol). Anglers comprise the target population, given their potential for exposure to
persistent environmental chemicals. The study’s primary environmental exposures are
listed in Section A.2. and Attachment5.a.. Study outcomes include time-to-pregnancy,
infertility (the absence of pregnancy following 12 months of trying), pregnancy loss,
gestation, and birth size. Three data collection instruments have been designed to capture
covariate data: a 25-minute baseline interview; 2-minute daily journal while attempting
pregnancy; and a 5-minute monthly journal for pregnant women. An illustration of data
collection activities is provided in Attachment 1.a. along with all data collection
instruments and related information in Attachments 1.b.-1.o. Couples can elect to
complete journals either online or via postage paid postcards as discussed in Supporting
Statement A.3. Research sites have been ensuring the completeness of reporting. The

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DCC has developed a web-based data management system that ensures the collection of
internally consistent and complete information with appropriate consideration of missing
data. Highly trained research nurses are instructing couples in the use of commercially
available home fertility monitors to aid them in timing intercourse to enhance the
probability of pregnancy and digital pregnancy test kits to identify postimplantation
pregnancies and pregnancy losses. Blood and urine samples are being collected at
baseline from both partners of the couple for measurement of the environmental
exposures including cotinine and phytoestrogens. Two semen samples are being
collected from male partners as a global measure of male fecundity and to quantify
contaminants in seminal fluid. Two saliva samples are being obtained from female
partners to measure cortisol levels as a marker of stress. This will allow us to evaluate
whether or not stress modifies the relation between environmental exposures and human
reproduction and development. Illustrations of the at home specimen collection kits,
fertility monitors and pregnancy test kits are included in Attachment 4.d..

The Longitudinal Investigation of Fertility and the Environment protocol incorporates a
number of quality control measures. Nurses and interviewing staff have received
extensive training regarding study equipment and procedures. Nurses are, in turn,
training participants in the use of fertility monitors and home pregnancy test kits.
Computer assisted interviewing software incorporate consistency checks and the DCC
will perform periodic checks for missing and inconsistent data. Problems, if identified,
are being referred to the research sites for resolution.

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Power calculations affirm our ability to detect meaningful differences for each of our
hypotheses (see Table 2). Our assumptions are based upon the empirical data from
prospective pregnancy studies conducted to date (Buck et al., 2004) and exposure
estimates from the CDC’s Second National Report on Human Exposure to Environmental
Chemical (2003) and the New York State Angler Cohort Study (Buck et al., 2003).
Based on a sample size of 400 couples completing the entire study protocol, we anticipate
that 320 (80%) couples will become pregnant of which 202 (63%) will have a live birth
(92% term birth and 8% preterm birth). Power calculations are based on two-tailed tests
with alpha = 0.05, and a mean PCB exposure of 4.0 ng/g serum.
Table 2. Summary of Estimated Statistical Power by Study Hypothesis
Study Outcome
Time-topregnancy
Infertility
Pregnancy
Loss**
Preterm delivery
Gestational age
Birth Weight

Sample
Minimal Effect Size
Size
400
a hazard ratio of 2.5 per unit
increase in PCB ng/g serum
400
OR = 1.50
320
OR = 1.57
202
202
202

OR=2.46
>0.26 weeks reduction in gestation
per unit increase in PCB
≈73 gram reduction in birth weight
per unit increase in PCB

Model*
Discrete
Time Cox
Logistic
Logistic
Logistic
Linear
Regression
Linear
Regression

Power
(%)
88
90
85
80
89
81

*Primary model, although others may be used.
**Power for early or human chorionic gonadotropin (hCG) detected pregnancies with home pregnancy test
kits.

B. 3. Methods to Maximize Response Rates and Deal with Nonresponse
As shown in Table 2, we expect a minimum of an 80% completion rate, which is
consistent with the response rates of other population-based prospective pregnancy
studies with preconception enrollment (Bonde et al. 1998; Brown et al. 1997; Buck et al.,
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2002; Ellish et al. 1996). Participants are receiving remuneration of $75 each for
providing biological specimens, as described in detail in Section A.9, which is well
within the range used in similar studies (Buck et al., 2004).

To enhance participation, introductory letters are being sent to potential study participants
followed by a personalized telephone call within two weeks to elicit participation and
establish eligibility. A public website is available (www.lifestudy.us) and individual
research sites have developed promotional materials tailored to their target populations.
Study sites have interviewers fluent in both English and Spanish. All study instruments
have been translated into Spanish.

An exhaustive literature review of incentives for groups traditionally underrepresented in
research identified several retention strategies that will be incorporated into the
Longitudinal Investigation of Fertility and the Environment protocol. These include: 1)
acquiring contact information for at least three contacts (friends or relatives of the
participants) once a signed release is obtained by the participating couple (Areán et al.,
2003; Boots Miller et al., 1998; Boys et al., 2003; Ribisl et al., 1996; Senturia et al.,
1998); 2) including change of address cards in the daily journals or on the website
(Napholz, 1998; Prinz et al., 2001; Ribisl et al., 1996; Senturia et al., 1998; 3) developing
an electronic database of all information regarding contact with participants (e.g. when
interviews and contacts were made, day and time of each to facilitate identification of a
“best time” to reach study participants (Ribisl et al., 1996; Senturia et al., 1998;
Shumaker et al., 2000); and 4) periodically sharing successful tracking techniques among

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research sites (Senturia et al., 1998). In addition, each site will establish and maintain a
trusting relationship with study participants by ensuring that: 1) they have a complete
understanding of the study requirements (Marmor et al., 1991; Senturia et al., 1998); 2)
there is a flexible interview and follow-up schedule (Areán et al., 2003; Janson et al.,
2001; Marmor et al., 1991; Prinz et al., 2001; Ribisl et al., 1996; Senturia et al., 1998); 3)
there is regular feedback about the study through a newsletter or website (Bender et al.,
2003; Janson et al., 2001; Marmor et al., 1991; Prinz et al., 2001; Wilcox et al., 1995); 4)
reminder cards or more personalized thank you notes or birthday cards are sent (Bender
et al., 2003; Boots Miller et al., 1998; Boys et al., 2003; Dennis & Neese, 2000; Marmor
et al., 1991; Napholz, 1998; Prinz et al., 2001; Senturia et al., 1998); and 5) there is
continuity of contact by making every effort to have the same nurse/interviewer contact
the couple over time (Boots Miller et al., 1998; Gilliss et al., 2001; Prinz et al., 2001;
Senturia et al., 1998). Lastly, the DCC has devised a tracking mechanism to keep
research sites informed about the status of complete, incomplete, pending, and missing
data. As described in Section A.9., a quality control plan has been developed to ensure
accuracy and reliability of data.

B. 4. Test of Procedures of Methods to be Undertaken

The NICHD undertook a series of preparatory tasks, including publishing literature
reviews of methodologic relevance (Buck et al., 2004; Rockett et al., 2004). Site PIs
have considerable expertise in conducting epidemiologic research on sensitive outcomes
in relation to environmental exposures. Dr. Anne Sweeney (PI of the Texas site) has

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successfully led two prospective pregnancy studies with preconception recruitment and
Dr. Timothy Wilcosky (PI of the Michigan site) is an expert in biomarkers, as evidenced
by his well-regarded textbook on the topic. Prior to coming to the NICHD, Dr. Germaine
Buck Louis (NICHD) also conducted a prospective pregnancy study with preconception
recruitment with funding from the ATSDR. This highly successful project enrolled
mothers planning pregnancy with follow-up of infants through age two years,
underscoring the willingness of families to participate in research on this important topic.
Dr. Steven Schrader (NIOSH) has conducted numerous field based studies focusing on
semen quality and has successfully utilized the methodologies included in this study
(>80% response).

Research sites obtained IRB approval to pilot test aspects of the proposed Longitudinal
Investigation of Fertility and the Environment protocol, particularly those pertaining to
the use of the digital fertility monitor. None of these pilot tests included more than eight
people. The results of the pilot work support the feasibility of using the monitor in
population-based research and are consistent with the communication that we have had
with two investigators currently in the field with studies that incorporate the use of the
monitor to: 1) aid couples in conceiving (Dr. Cecilia Pyper, Oxford University) and 2) to
assess prediction of cervical mucus (Dr. Joseph Stanford, University of Utah). No formal
evaluation of the digital pregnancy test kits was undertaken, as their utility for field
research is evidenced by their designation as an U.S. FDA class II medical device. A
historical presentation of the development and use of home pregnancy test kits, which

15

were first developed investigators at the NICHD, is available at:
www.history.nih.gov/exhibits/thinblueline/timeline.html.

B. 5. Individuals Consulted on Statistical Aspects and Individuals Collecting and/or
Analyzing Data

Intramural investigators at the NICHD have developed the analytic plan in collaboration
with the PIs from the two research sites. In doing so, a number of experts in
epidemiology, longitudinal data analysis, measurement error, and biomarkers have been
contacted. A list of these individuals is presented in Table 3.

Recruitment and all aspects of data collection have been done by two government
contractors: 1) RTI International in Michigan and 2) Texas A&M Rural School of Public
Health in Texas. Intramural investigators at the NICHD will do the data analysis. A
complete listing of these individuals is provided under the heading NICHD in Table 3.

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Table 3. Individuals who have Provided Statistical/Methodological Consultation to
the Longitudinal Investigation of Fertility and the Environment Study
Division of Epidemiology, Statistics, and Prevention Research

NICHD, DHHS
Germaine M. Buck Louis, PhD MS (PI)
Mark Klebanoff, MD MPH
Enrique Schisterman, PhD
Aiyi Liu, PhD
Courtney D. Lynch, PhD MPH
Leila Jackson, PhD MPH

301-496-6155
301-496-5267
301-435-6893
301-435-6953
301-435-6928
301-435-6918

Oklahoma University Health Science Center (consultants to TAMU)
Jennifer Peck, PhD
B. Mitchell Peck, PhD

405-271-2229 ext 48053
405-271-2114 ext 37082

RTI International
Tim Wilcosky, PhD (PI)
Jacquelyn Murphy
Roy Whitmore, PhD
Jennifer Staab, MPH

919-541-7367
202-728-2077
919-541-5809
919-541-6125

Texas A & M University Health Science Center (TAMU)
Anne Sweeney, PhD MS (PI)
Li Zhu, PhD
Ruzong Fan, PhD

979-458-0068
979-458-0079
979-845-3156

University of Oxford, UK
Cecilia Pyper, MD

01865 75971

University of Utah
Joseph B. Stanford, MD MSPH

801-587-3331

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References
Abma J, Chandra A, Mosher W, Peterson L, Piccinino L. Fertility, family planning, and
women's health: New data from the 1995 National Survey of Family Growth. NCHS
Vital Stats 23(19), 1997.
Areán PA, Alvidrez J, Nery R, Estes C, and Linkins K. Recruitment and retention of
older minorities in mental health services research. The Gerontologist 2003;43[1], 3644.
Axmon A. et al. Time to pregnancy and infertility among women with a high intake of
fish contaminated with persistent organochlorine compounds. Scand J Work Environ
Health 2000;26:199-206.
Belton, T., R. Roundy, and N. Weinstein. 1986. Urban fishermen: managing the risks of
toxic exposure. Environment. 28(9): 19-20, 30-37.
Bender BG, Ellison MC, Gleason M, Murphy JR, Sundstrom DA, and Szefler SJ.
Minimizing attrition in a long-term clinical trial of pediatric asthma. Annals of Allergy,
Asthma, & Immunology. 2003;91[2], 168-76.
Bonde JP, Hjollund NH, Jensen TK, Ernst E, Kolstad H, Henriksen TB et al. 1998. A
follow-up study of environmental and biologic determinants of fertility among 430
Danish first-pregnancy planners: design and methods. Reprod Toxicol 12:19-27.
Boots Miller BJ, Ribisl KM, Mowbray CT, Davidson WS, Walton MA, and Herman SE.
Methods of ensuring high follow-up rates: lessons from a longitudinal study of dual
diagnosed participants. Substance Use & Misuse. 1998;33[13], 2665-85.
Boys A, Marsden J, Stillwell G, Hatchings K, Griffiths P, and Farrell M. Minimizing
respondent attrition in longitudinal research: practical implications from a cohort study
of adolescent drinking. Journal of Adolescence. 2003;26[3], 363-73.
Brown JE, Jacobs DRJ, Barosso GM, Potter JD, Hannan PJ, Kopher RA et al. 1997.
Recruitment, retention and characteristics of women in a prospective study of
preconceptional risks to reproductive outcomes: experience of the Diana Project. Paediatr
Perinat Epidemiol 11:345-358.
Buck G, Vena JE, Greizerstein HB, Weiner JM, McGuinness B, Mendola P et al. 2002.
PCB Congeners and pesticides and female fecundity, New York State Angler Prospective
Pregnancy Study. Environmental Toxicology and Pharmacology 12:83-92.
Buck GM, Tee GP, Fitzgerald EF, Vena JE, Weiner JM, Swanson M, Msall M. Maternal
fish consumption and infant birth size and gestation: New York State Angler Cohort
Study. Environ Health 2003;2:1-9 or http://www.enjournal.net/content.

18

Buck GM, Lynch CD, Stanford JB, Sweeney AM, Schieve LA, Rockett JC, Selevan SG,
Schrader SM. Prospective pregnancy study designs for assessing reproductive and
developmental toxicants. Environ Health Perspect 2004;112:79-86.
Centers for Disease Control and Prevention. Second National Report on Human
Exposure to Environmental Chemicals. NCEH Pub. No.02-0716. Atlanta, Georgia,
2003.
Chapin RE, Robbins WA, Schieve LA, Sweeney AM, Tabacova SA, Tomashek KM. Off
to a good start: the influence of pre- and peri-conceptional exposures, parental fertility,
and nutrition on children's health. Environ Health Perspect 2004;112;69-78.
Cohen SB, DiGaetano R, Waksberg J. Sample Design of the National Medical
Expenditure Survey-Household Component. Proceedings of the Survey Research
Methods Section, American Statistical Association, 1987.
Dennis BP and Neese JB. Recruitment and retention of African American elders into
community-based research: lessons learned. Archives of Psychiatric Nursing.
2000;14[1], 3-11.
Ellish NJ, Saboda K, O'Connor J, Nasca PC, Stanek EJ, Boyle C. 1996. A prospective
study of early pregnancy loss. Hum Reprod 11:406-412.
Gilliss CL, Lee KA, Gutierrez Y, Taylor D, Beyene Y, Neuhaus J, and Murrell N.
Recruitment and retention of healthy minority women into community-based longitudinal
research. Journal of Women’s Health & Gender-Based Medicine. 10[1], 77-85. 2001.
Janson SL, Alioto ME, and Boushey HA. Attrition and retention of ethnically diverse
subjects in a multicenter randomized controlled research trial. Controlled Clinical Trials.
22[6 Suppl], 236S-43S. 2001.
Marmor JK, Oliveria SA, Donahue RP, Garrahie EJ, White MJ, Moore LL, and Ellison
RC. Factors encouraging cohort maintenance in a longitudinal study. Journal of Clinical
Epidemiology. 44[6], 531-35. 1991.
Napholz L. Enhancing research participation and retention for three ethnically diverse
groups. Journal of Cultural Diversity. 1998;5[4], 117-9.
Prinz RJ, Smith EP, Dumas JE, Laughlin JE, White DW, and Barron R. Recruitment and
retention of participants in prevention trials involving family-based interventions.
American Journal of Prevention Medicine. 2001;20[1S], 31-36.
Ribisl KM, Walton MA, Mowbray CT, Luke DA, Davidson II WS, and BootsMiller BJ.
Minimizing participant attrition in panel studies through the use of effective retention and
tracking strategies: review and recommendations. Education and Program Planning.
1996;19[1], 1-25.

19

Rockett JC, Buck GM, Lynch CD, Perreault SD. The value of home-based specimen
collection of biospecimens in reproductive epidemiology. 2004;112:94-104.
Slama R, Ducot B, Carstensen L, Lorente C, de La Rochebrochard E, Leridon H, Keiding
N, Bouyer J. Feasibility of the current duration approach to studying human fecundity.
Epidemiol 2006;17:440-449.
Senturia YD, McNiff Mortimer K, Baker D, Gergen P, Mitchell H, Joseph C, and
Wedner HJ. Successful techniques for retention of study participants in an inner-city
population. Controlled Clinical Trials. 1998;19[6], 544-54.
Sexton K. Sociodemographic aspects of human susceptability to toxic chemicals: do class
and race matter for realistic risk assessment. Environ Toxicol Pharmacol 1997;4:261-269.
Singh RP, Petroni RJ, and Allen TM. Oversampling in panel surveys. Proceedings of
the Survey Research Methods Section, American Statistical Association, 1994.
Stephen EH, Chandra A. Updated projections of infertility in the United States: 19952025. Fertil Steril 1998;70:30-34.
Sweeney AM, Meyer MR, Mills JL, Aarons JH, LaPorte RE. Evaluation of recruitment
strategies for prospective studies of spontaneous abortion. J Occup Med 1989;31:980985.
West, P.C. 1992. Invitation to poison? Detroit minorities and toxic fish consumption from
the Detroit River. In: Race and the Incidence of Environmental Hazards. B. Bryant, P.
Mohai, eds.Westview Press. p 96-99.
Wilcox AJ, Weinberg CR, Baird DD. Timing of sexual intercourse in relation to
ovulation: effects on the probability of conception, survival of the pregnancy and sex of
the baby. New Engl J Med 1995;333:1517-1521.
Wilcox AJ, Weinberg CR, O'Connor JF, Baird DD, Schlatterer JP, Canfield RE et al.
Incidence of early loss of pregnancy. N Engl J Med 1988;319:189-194.

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