Recruitment prior to conception for pregnancy studies: a systematic review and meta-analysis
File(s)
Published version
Author(s)
Type
Journal Article
Abstract
Objective
Pregnancy outcomes may be improved by optimizing preconception health; however, designing preconception research studies presents distinct challenges. These include estimating feasible recruitment, attrition, and expected pregnancy rates. We systematically reviewed existing preconception studies to quantify recruitment rates, retention, and pregnancies to inform feasibility assessments and sample size calculations for future preconception and pregnancy-related research.
Data Sources
NHS Knowledge Hub, TRIP database, Cochrane Library, PubMed, MEDLINE, Embase, CINAHL, Emcare, Web of Science, Scopus, ASSIA, and PsycINFO were searched (database inception-September 2025).
Study Eligibility Criteria
Eligible studies reported recruitment of non-pregnant women intending to conceive into studies reporting at least one pregnancy outcome.
Study Appraisal and Synthesis Methods
Risk of bias and quality assessment were performed using the Newcastle-Ottawa Scale and Cochrane Risk of Bias Tool, followed by the GRADE framework. Statistical analysis was performed in R v4.4.1.
Results
79 studies (n=117,603 participants; n=53,838 pregnancies) were included. Overall, risk of bias was fair across studies. The heterogeneity across all meta-analyses was high.
Recruitment via healthcare settings yielded higher weekly recruitment than other methods (median 9 participants/week, IQR 4-19), compared with studies using only non-healthcare-based recruitment methods (2, IQR 2-4). Weekly recruitment was higher in larger studies and in low- and middle-income countries compared to high-income countries.
Attrition prior to conception was lower in observational than interventional studies and among those with fertility issues compared to those with other medical comorbidities. Among participants who conceived, retention during pregnancy was high across all studies (97.7%, IQR 95.2-99.0), with higher retention in interventional than observational studies.
Conclusions
This review provides a quantitative synthesis of recruitment and retention patterns in preconception research, addressing a critical but understudied period to improve maternal and child health. We found that participant characteristics, recruitment strategy, and study design significantly influence recruitment rates, preconception attrition, and pregnancy retention, with important implications for feasibility assessment, anticipated loss to follow-up, and sample size estimation. Our findings highlight the need for recruitment of diverse populations and methodological tools tailored to preconception research. These findings offer empirically grounded parameters to support the design of more efficient, inclusive, and adequately powered preconception and pregnancy-related studies.
Pregnancy outcomes may be improved by optimizing preconception health; however, designing preconception research studies presents distinct challenges. These include estimating feasible recruitment, attrition, and expected pregnancy rates. We systematically reviewed existing preconception studies to quantify recruitment rates, retention, and pregnancies to inform feasibility assessments and sample size calculations for future preconception and pregnancy-related research.
Data Sources
NHS Knowledge Hub, TRIP database, Cochrane Library, PubMed, MEDLINE, Embase, CINAHL, Emcare, Web of Science, Scopus, ASSIA, and PsycINFO were searched (database inception-September 2025).
Study Eligibility Criteria
Eligible studies reported recruitment of non-pregnant women intending to conceive into studies reporting at least one pregnancy outcome.
Study Appraisal and Synthesis Methods
Risk of bias and quality assessment were performed using the Newcastle-Ottawa Scale and Cochrane Risk of Bias Tool, followed by the GRADE framework. Statistical analysis was performed in R v4.4.1.
Results
79 studies (n=117,603 participants; n=53,838 pregnancies) were included. Overall, risk of bias was fair across studies. The heterogeneity across all meta-analyses was high.
Recruitment via healthcare settings yielded higher weekly recruitment than other methods (median 9 participants/week, IQR 4-19), compared with studies using only non-healthcare-based recruitment methods (2, IQR 2-4). Weekly recruitment was higher in larger studies and in low- and middle-income countries compared to high-income countries.
Attrition prior to conception was lower in observational than interventional studies and among those with fertility issues compared to those with other medical comorbidities. Among participants who conceived, retention during pregnancy was high across all studies (97.7%, IQR 95.2-99.0), with higher retention in interventional than observational studies.
Conclusions
This review provides a quantitative synthesis of recruitment and retention patterns in preconception research, addressing a critical but understudied period to improve maternal and child health. We found that participant characteristics, recruitment strategy, and study design significantly influence recruitment rates, preconception attrition, and pregnancy retention, with important implications for feasibility assessment, anticipated loss to follow-up, and sample size estimation. Our findings highlight the need for recruitment of diverse populations and methodological tools tailored to preconception research. These findings offer empirically grounded parameters to support the design of more efficient, inclusive, and adequately powered preconception and pregnancy-related studies.
Date Issued
2026-07-01
Date Acceptance
2026-01-29
Citation
American Journal of Obstetrics and Gynecology, 2026, 235 (1), pp.22-32
ISSN
0002-9378
Publisher
Elsevier BV
Start Page
22
End Page
32
Journal / Book Title
American Journal of Obstetrics and Gynecology
Volume
235
Issue
1
Copyright Statement
© 2026 The Author(s). Published by Elsevier Inc. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).
License URL
Identifier
https://www.ncbi.nlm.nih.gov/pubmed/41654246
PII: S0002-9378(26)00066-9
Subjects
Clinical Trials
Maternal Health
Meta-analysis
Participant Dropout
Preconception
Preconception Care
Pregnancy
Pregnancy Outcomes
Recruitment
Research Design
Retention
Systematic Review
Publication Status
Published
Coverage Spatial
United States
Date Publish Online
2026-02-05