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<meta name="description" content="The low assessed-to-enrolled ratio found in this study suggested that researchers are casting a large net for patient recruitment. The relatively high eligible-to-randomized ratio suggested that most individuals are willing to participate in obstetrical RCTs. This finding was at odds with previous c …"><meta name="keywords" content="pmid:35031522, doi:10.1016/j.ajogmf.2022.100564, Letter, Review, Kelly C Ditter, Ellen H Crowe, Stephen Wagner, Gynecology*, Humans, Obstetrics*, Patient Selection, Randomized Controlled Trials as Topic, Research Design, PubMed Abstract, NIH, NLM, NCBI, National Institutes of Health, National Center for Biotechnology Information, National Library of Medicine, MEDLINE"><meta name="robots" content="index,nofollow,noarchive"><meta property="og:title" content="Obstetrical randomized controlled trials: individuals screened, approached, and enrolled - PubMed"><meta property="og:url" content="https://pubmed.ncbi.nlm.nih.gov/35031522/"><meta property="og:description" content="The low assessed-to-enrolled ratio found in this study suggested that researchers are casting a large net for patient recruitment. The relatively high eligible-to-randomized ratio suggested that most individuals are willing to participate in obstetrical RCTs. This finding was at odds with previous c …"><meta property="og:image" content="https://cdn.ncbi.nlm.nih.gov/pubmed/persistent/pubmed-meta-image-v2.jpg"><meta property="og:image:secure_url" content="https://cdn.ncbi.nlm.nih.gov/pubmed/persistent/pubmed-meta-image-v2.jpg"><meta property="og:type" content="website"><meta property="og:site_name" content="PubMed"><meta name="twitter:domain" content="pubmed.ncbi.nlm.nih.gov"><meta name="twitter:card" content="summary_large_image"><meta name="twitter:title" content="Obstetrical randomized controlled trials: individuals screened, approached, and enrolled - PubMed"><meta name="twitter:url" content="https://pubmed.ncbi.nlm.nih.gov/35031522/"><meta name="twitter:description" content="The low assessed-to-enrolled ratio found in this study suggested that researchers are casting a large net for patient recruitment. The relatively high eligible-to-randomized ratio suggested that most individuals are willing to participate in obstetrical RCTs. This finding was at odds with previous c …"><meta name="twitter:image" content="https://cdn.ncbi.nlm.nih.gov/pubmed/persistent/pubmed-meta-image-v2.jpg">
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<label for="email-include-supplemental" class="email-include-supplemental-label">MeSH and other data</label>
</div>
<div class="form-field recaptcha ">
<div class="g-recaptcha" id="id-recaptcha" data-sitekey="6LfsWHMdAAAAAClKbtOpjQ2pMjgsGxvv7NdZW9uI"></div>
</div>
<div id="captcha-error-message" class="usa-input-error-message captcha-validation-message" role="alert"></div>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Sending..."
data-ga-category="save_share"
data-ga-action="email"
data-ga-label="send">
Send email
</button>
<button class="action-panel-cancel"
aria-label="Close 'Email citations' panel"
ref="linksrc=close_email_panel"
aria-controls="email-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="email"
data-ga-label="cancel">
Cancel
</button>
</div>
<input type="hidden" name="email-search-details" value="" />
<input type="hidden" name="email-search-details-hash" value="0e42663a6c3bd85498fcb88798998fed7bfdc45d457db35281e41afe13cc0524" />
</form>
</div>
</div>
<div id="collections-action-panel"
class="collections-action-panel action-panel in-progress-dots-panel"
aria-hidden="true"
data-collections-open-panel-enabled="false"
data-collections-open-panel-url-hash="#open-collections-panel">
<div class="inner-wrap">
<h3 class="action-panel-heading">
Add to Collections
</h3>
<form id="collections-action-panel-form"
class="collections-action-panel-form action-panel-content action-form action-panel-smaller-selectors"
data-existing-collections-url="/list-existing-collections/"
data-add-to-existing-collection-url="/add-to-existing-collection/"
data-create-and-add-to-new-collection-url="/create-and-add-to-new-collection/"
data-get-article-ids-by-search-url="/get-article-ids-by-search/"
data-myncbi-max-collection-name-length="100"
data-add-to-collection-max-amount="1000"
data-collections-root-url="https://www.ncbi.nlm.nih.gov/myncbi/collections/">
<input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS">
<div class="choice-group" role="radiogroup">
<ul class="radio-group-items">
<li>
<input type="radio"
id="collections-action-panel-new"
class="collections-new"
name="collections"
value="new"
data-ga-category="save_share"
data-ga-action="collections"
data-ga-label="collections_radio_new">
<label for="collections-action-panel-new">Create a new collection</label>
</li>
<li>
<input type="radio"
id="collections-action-panel-existing"
class="collections-existing"
name="collections"
value="existing"
checked="true"
data-ga-category="save_share"
data-ga-action="collections"
data-ga-label="collections_radio_existing">
<label for="collections-action-panel-existing">Add to an existing collection</label>
</li>
</ul>
</div>
<div class="controls-wrapper">
<div class="action-panel-control-wrap new-collections-controls">
<label for="collections-action-panel-add-to-new" class="action-panel-label required-field-asterisk">
Name your collection:
</label>
<input
type="text"
name="add-to-new-collection"
id="collections-action-panel-add-to-new"
class="collections-action-add-to-new"
pattern="[^&quot;&amp;=&lt;&gt;\/]*" title="The following characters are not allowed in the Name field: &quot;&amp;=&lt;&gt;/"
maxlength="100"
data-ga-category="save_share"
data-ga-action="create_collection"
data-ga-label="non_favorties_collection">
<div class="collections-new-name-too-long usa-input-error-message selection-validation-message">
Name must be less than 100 characters
</div>
</div>
<div class="action-panel-control-wrap existing-collections-controls">
<label for="collections-action-panel-add-to-existing" class="action-panel-label">
Choose a collection:
</label>
<select id="collections-action-panel-add-to-existing"
class="action-panel-selector collections-action-add-to-existing"
data-ga-category="save_share"
data-ga-action="select_collection"
data-ga-label="($('#collections-action-add-to-existing').val() === 'Favorites') ? 'Favorites' : 'non_favorites_collection'">
</select>
<div class="collections-retry-load-on-error usa-input-error-message selection-validation-message">
Unable to load your collection due to an error<br>
<a href="#">Please try again</a>
</div>
</div>
</div>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Adding..."
data-pinger-ignore
data-ga-category="save_share"
data-ga-action="collections"
data-ga-label="add">
Add
</button>
<button class="action-panel-cancel"
aria-label="Close 'Add to Collections' panel"
ref="linksrc=close_collections_panel"
aria-controls="collections-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="collections"
data-ga-label="cancel">
Cancel
</button>
</div>
</form>
</div>
</div>
<div id="bibliography-action-panel"
class="bibliography-action-panel action-panel in-progress-dots-panel"
aria-hidden="true"
data-bibliography-open-panel-enabled="false"
data-bibliography-open-panel-url-hash="#open-bibliography-panel">
<div class="inner-wrap">
<h3 class="action-panel-heading">
Add to My Bibliography
</h3>
<form id="bibliography-action-panel-form"
class="bibliography-action-panel-form action-panel-content action-form action-panel-smaller-selectors"
data-add-to-bibliography-max-amount="100"
data-add-to-bibliography-batch-size="10"
data-bibliography-delegates-url="/list-bibliography-delegates/"
data-add-to-bibliography-url="/add-to-bibliography/"
data-get-article-ids-by-search-url="/get-article-ids-by-search/"
data-mybib-root-url="https://www.ncbi.nlm.nih.gov/myncbi/collections/mybibliography/">
<input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS">
<div class="action-panel-control-wrap bibliographies-controls">
<div class="choice-group">
<ul class="bibliographies-action-add radio-group-items">
<li>
<input name="bibliography" id="my-bibliography" class="my-bibliography" type="radio" checked/>
<label for="my-bibliography">My Bibliography</label>
</li>
</ul>
</div>
</div>
<div class="bibliographies-retry-load-on-error usa-input-error-message selection-validation-message">
Unable to load your delegates due to an error<br>
<a href="#">Please try again</a>
</div>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Adding..."
data-pinger-ignore>
Add
</button>
<button class="action-panel-cancel"
aria-label="Close 'Add to bibliography' panel"
ref="linksrc=close_bibliography_panel"
aria-controls="bibliography-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="mybib"
data-ga-label="cancel">
Cancel
</button>
</div>
</form>
</div>
</div>
<div id="saved-search-action-panel" class="saved-search-action-panel action-panel " aria-hidden="true"
data-saved-search-open-panel-enabled="false"
data-saved-search-open-panel-url-hash="#open-saved-search-panel">
<div class="inner-wrap">
<h2 class="action-panel-heading">
Your saved search
</h2>
<form id="saved-search-action-panel-form"
class="saved-search-action-panel-form action-panel-content action-form"
data-create-saved-search-url="/create-saved-search/"
data-try-search-terms-url="/try-search-term/"
data-saved-search-root-url="https://www.ncbi.nlm.nih.gov/myncbi/searches/">
<input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS">
<div class="action-panel-control-wrap">
<label for="saved-search-name" class="action-panel-label saved-search-name-label required-field-asterisk">
Name of saved search:
</label>
<input maxlength="200"
type="text"
name="saved-search-name"
id="saved-search-name"
class="saved-search-name"
value=""
required
pattern="[^&quot;&amp;=&lt;&gt;\/]*" title="The following characters are not allowed in the Name field: &quot;&amp;=&lt;&gt;/">
</div>
<div class="action-panel-control-wrap">
<label for="saved-search-term" class="action-panel-label required-field-asterisk">
Search terms:
</label>
<textarea name="saved-search-term" id="saved-search-term" class="saved-search-term" required></textarea>
</div>
<div class="test-search-term-wrap">
<a href="#" class="try-search-term">Test search terms</a>
</div>
<div class="choice-group action-panel-extra-margin-top">
<span class="action-panel-label" id="fieldset-label">
Would you like email updates of new search results?
</span>
<fieldset id="saved-search-alert" aria-describedby="fieldset-label">
<legend class="usa-sr-only">Saved Search Alert Radio Buttons</legend>
<ul class="radio-group-items">
<li>
<input type="radio" id="saved-search-alert-yes" class="saved-search-alert-yes" name="saved-search-alert" value="yes" checked>
<label for="saved-search-alert-yes" class="action-panel-label">Yes</label>
</li>
<li>
<input aria-label="No radio input" type="radio" id="saved-search-alert-no" class="saved-search-alert-no" name="saved-search-alert" value="no">
<label for="saved-search-alert-no" class="action-panel-label">No</label>
</li>
</ul>
</fieldset>
</div>
<div class="alert-schedule-wrap">
<div class="action-panel-control-wrap">
<label class="action-panel-label">
Email:
</label>
<span aria-label="Email address" id="saved-search-email" class="action-panel-label"><span class="action-panel-label-bold"></span> (<a class="myncbi-account-settings" href="https://www.ncbi.nlm.nih.gov/account/settings/">change</a>)</span>
</div>
<div class="action-panel-control-wrap action-panel-extra-margin-top">
<label for="saved-search-frequency" class="action-panel-label">
Frequency:
</label>
<select id="saved-search-frequency" class="no-border-panel-selector saved-search-frequency">
<option value="monthly">Monthly</option>
<option value="weekly">Weekly</option>
<option value="daily">Daily</option>
</select>
</div>
<div class="action-panel-control-wrap saved-search-monthly-additional">
<label for="saved-search-monthly-on-day" class="action-panel-label">
Which day?
</label>
<select id="saved-search-monthly-on-day" class="no-border-panel-selector">
<option value="Sunday">The first Sunday</option>
<option value="Monday">The first Monday</option>
<option value="Tuesday">The first Tuesday</option>
<option value="Wednesday">The first Wednesday</option>
<option value="Thursday">The first Thursday</option>
<option value="Friday">The first Friday</option>
<option value="Saturday">The first Saturday</option>
<option value="day">The first day</option>
<option value="weekday">The first weekday</option>
</select>
</div>
<div class="action-panel-control-wrap saved-search-weekly-additional">
<label for="saved-search-weekly-on-day" class="action-panel-label">
Which day?
</label>
<select id="saved-search-weekly-on-day" class="no-border-panel-selector saved-search-weekly-on-day">
<option value="Sunday">Sunday</option>
<option value="Monday">Monday</option>
<option value="Tuesday">Tuesday</option>
<option value="Wednesday">Wednesday</option>
<option value="Thursday">Thursday</option>
<option value="Friday">Friday</option>
<option value="Saturday">Saturday</option>
</select>
</div>
<div class="action-panel-control-wrap">
<label for="saved-search-report" class="action-panel-label">
Report format:
</label>
<select id="saved-search-report" class="no-border-panel-selector saved-search-report">
<option value="DocSum">Summary</option>
<option value="DocSumText">Summary (text)</option>
<option value="Abstract">Abstract</option>
<option value="AbstractText">Abstract (text)</option>
<option value="MEDLINE">PubMed</option>
</select>
</div>
<div class="action-panel-control-wrap">
<label for="saved-search-amount" class="action-panel-label">
Send at most:
</label>
<select id="saved-search-amount" class="no-border-panel-selector saved-search-amount">
<option value="1">1 item</option>
<option value="5" selected>5 items</option>
<option value="10">10 items</option>
<option value="20">20 items</option>
<option value="50">50 items</option>
<option value="100">100 items</option>
<option value="200">200 items</option>
</select>
</div>
<div>
<input type="checkbox" id="saved-search-send-if-no-result" class="saved-search-send-if-no-result" name="saved-search-send-if-no-result">
<label for="saved-search-send-if-no-result" class="action-panel-label smaller-checkbox">
Send even when there aren't any new results
</label>
</div>
<div class="action-panel-control-wrap option-text-in-email-wrap">
<label for="saved-search-email-text" class="action-panel-label">
Optional text in email:
</label>
<textarea name="saved-search-email-text"
id="saved-search-email-text"
class="saved-search-email-text"></textarea>
</div>
</div>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Saving..."
data-ga-category="save_share"
data-ga-action="alert"
data-ga-label="save">
Save
</button>
<button class="action-panel-cancel"
aria-label="Close 'Your saved search' panel"
ref="linksrc=close_saved_search_panel"
aria-controls="saved-search-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="alert"
data-ga-label="cancel">
Cancel
</button>
</div>
</form>
</div>
</div>
<div id="citation-manager-action-panel" class="citation-manager-action-panel action-panel" aria-hidden="true">
<div class="inner-wrap">
<h2 class="action-panel-heading">
Create a file for external citation management software
</h2>
<form id="citation-manager-action-panel-form"
class="action-panel-content action-form"
action="/results-export-ids/"
data-by-search-action="/results-export-search-data/"
data-by-ids-action="/results-export-ids/"
method="post"
data-by-search-method="post"
data-by-ids-method="post">
<input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS">
<input name="results-format" type="hidden" value="pubmed"/>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Sending..."
data-ga-category="save_share"
data-ga-action="citation_manager"
data-ga-label="save">
Create file
</button>
<button class="action-panel-cancel"
aria-label="Close 'Send citations to citation manager' panel"
ref="linksrc=close_citation_manager_panel"
aria-controls="citation-manager-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="citation_manager"
data-ga-label="cancel">
Cancel
</button>
</div>
</form>
</div>
</div>
<div id="rss-action-panel" class="rss-action-panel action-panel " aria-hidden="true">
<div class="inner-wrap">
<h2 class="action-panel-heading">
Your RSS Feed
</h2>
<form id="rss-action-panel-form"
class="rss-action-panel-form action-panel-content action-form"
data-create-rss-feed-url="/create-rss-feed-url/"
data-search-form-term-value="">
<input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS">
<div class="action-panel-control-wrap">
<label for="rss-name" class="action-panel-label required-field-asterisk">
Name of RSS Feed:
</label>
<input maxlength="200"
placeholder="Name"
type="text"
name="rss-name"
id="rss-name"
class="rss-name"
value=''
required
pattern="[^&quot;&amp;=&lt;&gt;\/]*" title="The following characters are not allowed in the Name field: &quot;&amp;=&lt;&gt;/">
</div>
<div class="rss-limit-wrap">
<div class="action-panel-control-wrap action-panel-extra-margin-top">
<label for="rss-limit" class="action-panel-label">
Number of items displayed:
</label>
<select id="rss-limit" class="no-border-panel-selector rss-limit">
<option value="5">5</option>
<option value="10">10</option>
<option value="15" selected="selected">15</option>
<option value="20">20</option>
<option value="50">50</option>
<option value="100">100</option>
</select>
</div>
</div>
<div class="action-panel-actions">
<button class="action-panel-submit"
type="submit"
data-loading-label="Creating..."
data-ga-category="save_share"
data-ga-action="alert"
data-ga-label="save">
Create RSS
</button>
<button class="action-panel-cancel"
aria-label="Close 'Your RSS' panel"
ref="linksrc=close_rss_panel"
aria-controls="rss-action-panel"
aria-expanded="false"
data-ga-category="save_share"
data-ga-action="alert"
data-ga-label="cancel">
Cancel
</button>
</div>
<div class="action-panel-control-wrap rss-link-copy-wrap">
<label for="rss-link" class="usa-sr-only">RSS Link</label>
<input placeholder="Your RSS Feed Link" type="text" name="rss-link" id="rss-link" class="rss-link" title="RSS Link">
<button
type="button"
disabled
class="rss-link-copy-button disabled"
data-ga-category="save_share"
data-ga-action="rss"
data-ga-label="copy">
Copy
</button>
</div>
</form>
</div>
</div>
</div>
</div>
<div class="article-page" id="article-page" data-article-pmid="35031522">
<aside class="page-sidebar">
<div class="inner-wrap">
<div class="full-text-links">
<div class="full-view">
<h3 class="title">
Full text links
</h3>
<div class="full-text-links-list">
<a class="link-item
dialog-focus"
href="https://linkinghub.elsevier.com/retrieve/pii/S2589-9333(22)00004-0"
target="_blank"
rel="noopener"
ref="linksrc=fulltextorjournal_fulltext&amp;is_pmc=False&amp;PrId=3048&amp;itool=Abstract-def&amp;log$=linkouticon&amp;uid=35031522&amp;db=pubmed&amp;nlmid=101746609"
title="See full text options at Elsevier Science"
data-ga-category="full_text"
data-ga-action="Elsevier Science"
data-ga-label="35031522"
><img src="https://cdn.ncbi.nlm.nih.gov/corehtml/query/egifs/https:--linkinghub.elsevier.com-ihub-images-PubMedLink.gif" alt="Elsevier Science full text link"><span class="text">
Elsevier Science
</span></a>
</div>
</div>
<div class="short-view">
<a href="#" class="full-text-links-button full-text-links-dialog-trigger">
Full text links
</a>
</div>
</div>
<div class="actions-buttons sidebar"><h3 class="title">Actions</h3><div class="inner-wrap"><button class="citation-button citation-dialog-trigger"
aria-label="Open dialog with citation text in different styles"
data-ga-category="save_share"
data-ga-action="cite"
data-ga-label="open"
data-all-citations-url="/35031522/citations/"
data-citation-style="nlm"
data-pubmed-format-link="/35031522/export/"><span class="button-label">Cite</span></button><link type="text/css" href="ncbi-overlay-block/src/overlay-block.css"><div class="collections-button-container" data-article-id="35031522" data-article-db="pubmed"><button class="collections-button collections-dialog-trigger"
aria-label="Save article in MyNCBI collections."
data-ga-category="collections_button"
data-ga-action="click"
data-ga-label="collections_button"
data-collections-open-dialog-enabled="false"
data-collections-open-dialog-url="https://account.ncbi.nlm.nih.gov/?back_url=https%3A%2F%2Fpubmed.ncbi.nlm.nih.gov%2F35031522%2F%23open-collections-dialog"
data-in-collections="false"><span class="button-label">Collections</span></button><div class="overlay" role="dialog"><div id="collections-action-dialog"
class="dialog collections-dialog"
aria-hidden="true"><div class="title">Add to Collections</div><div class="collections-action-panel action-panel"><form id="collections-action-dialog-form"
class="collections-action-panel-form action-panel-content action-form action-panel-smaller-selectors"
data-existing-collections-url="/list-existing-collections/"
data-add-to-existing-collection-url="/add-to-existing-collection/"
data-create-and-add-to-new-collection-url="/create-and-add-to-new-collection/"
data-myncbi-max-collection-name-length="100"
data-collections-root-url="https://www.ncbi.nlm.nih.gov/myncbi/collections/"><input type="hidden" name="csrfmiddlewaretoken" value="zsOuIqMEMj9eR02GodtEDA3tUTBBSC7yQfyzlgf0mUWILr8w1w6G7Iz7sXjNLdFS"><div class="choice-group" role="radiogroup"><ul class="radio-group-items"><li><input type="radio"
id="collections-action-dialog-new"
class="collections-new"
name="collections"
value="new"
data-ga-category="collections_button"
data-ga-action="click"
data-ga-label="collections_radio_new"><label for="collections-action-dialog-new">Create a new collection</label></li><li><input type="radio"
id="collections-action-dialog-existing"
class="collections-existing"
name="collections"
value="existing"
checked="true"
data-ga-category="collections_button"
data-ga-action="click"
data-ga-label="collections_radio_existing"><label for="collections-action-dialog-existing">Add to an existing collection</label></li></ul></div><div class="controls-wrapper"><div class="action-panel-control-wrap new-collections-controls"><label for="collections-action-dialog-add-to-new" class="action-panel-label required-field-asterisk">
Name your collection:
</label><input
type="text"
name="add-to-new-collection"
id="collections-action-dialog-add-to-new"
class="collections-action-add-to-new"
pattern="[^&quot;&amp;=&lt;&gt;\/]*" title="The following characters are not allowed in the Name field: &quot;&amp;=&lt;&gt;/"
maxlength="100"
data-ga-category="collections_button"
data-ga-action="create_collection"
data-ga-label="non_favorties_collection"><div class="collections-new-name-too-long usa-input-error-message selection-validation-message">
Name must be less than 100 characters
</div></div><div class="action-panel-control-wrap existing-collections-controls"><label for="collections-action-dialog-add-to-existing" class="action-panel-label">
Choose a collection:
</label><select id="collections-action-dialog-add-to-existing"
class="action-panel-selector collections-action-add-to-existing"
data-ga-category="collections_button"
data-ga-action="select_collection"
data-ga-label="($('.collections-action-add-to-existing').val() === 'Favorites') ? 'Favorites' : 'non_favorites_collection'"></select><div class="collections-retry-load-on-error usa-input-error-message selection-validation-message">
Unable to load your collection due to an error<br><a href="#">Please try again</a></div></div></div><div class="action-panel-actions"><button class="action-panel-submit"
type="submit"
data-loading-label="Adding..."
data-pinger-ignore
data-ga-category="collections_button"
data-ga-action="click"
data-ga-label="add">
Add
</button><button class="action-panel-cancel"
aria-label="Close 'Add to Collections' panel"
ref="linksrc=close_collections_panel"
aria-controls="collections-action-panel"
aria-expanded="false"
data-ga-category="collections_button"
data-ga-action="click"
data-ga-label="cancel">
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Background:
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The use of randomized clinical trials (RCTs) is predicated on the idea that the study group is representative of the overall clinical population; however, recent studies have suggested that this may not be the case in obstetrics.<sup>1</sup><sup>,</sup><sup>2</sup> The generalizability of several seminal obstetrical RCTs, including the A Randomized Trial of Induction Versus Expectant Management trial, has been questioned because of the high ratio of assessed-to-enrolled individuals.<sup>3</sup> Although difficulty in recruitment for obstetrical RCTs is known,<sup>4</sup> it has been postulated that this high ratio increases the likelihood of the study population not being truly representative. Our primary objective was to analyze the assessed-to-enrolled ratio in contemporary obstetrical RCTs.
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Study design:
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During a 4-year period (January 2017 to December 2020), we identified all obstetrical RCTs published in 6 journals (The New England Journal of Medicine, Journal of the American Medical Association, Lancet, American Journal of Obstetrics &amp; Gynecology, British Journal of Obstetrics and Gynaecology, and Obstetrics &amp; Gynecology). The journals were manually reviewed by 2 coauthors to ensure all obstetrical RCTs were identified and abstracted accurately. Reported patient recruitment data, per Consolidated Standards of Reporting Trials recommendations,<sup>5</sup> were abstracted from each RCT. Based on the primary outcome of the study, the purpose of the trial was categorized as preventative or treatment. Medians were compared using Wilcoxon rank-sum testing, and P&lt;.05 was considered significant.
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Results:
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Of 240 obstetrical RCTs that were identified, 193 (80%) reported data on the number of individuals screened and recruited. The median number of individuals screened per trial was 850 (interquartile range [IQR], 323-2582), of which 348 were eligible (IQR, 201-1347) and 300 (IQR, 133-894) were randomized. There was no difference in trials based internationally or in the United States (P=.26). Compared with preventative RCTs, the trials that had treatment as the primary outcome were significantly more likely to screen a larger number of individuals for eligibility (P&lt;.01) and subsequently randomize (P&lt;.02). There was no difference in the median number of individuals who declined enrollment between trials with prevention or treatment as their objective (P=.12). More individuals were lost to follow-up in trials with prevention as the primary outcome (P&lt;.01), although the median number lost was low at 3 (IQR, 0-21).
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Conclusion:
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The low assessed-to-enrolled ratio found in this study suggested that researchers are casting a large net for patient recruitment. The relatively high eligible-to-randomized ratio suggested that most individuals are willing to participate in obstetrical RCTs. This finding was at odds with previous critiques of obstetrical RCTs that had called in to question study results secondary to high eligible-to-randomized ratios. Further research into how patients are recruited and counseled is indicated, to explore this variation. The ratio of patients assessed for study eligibility to patients enrolled in preventative vs treatment RCTs was not substantially different. Based on this result, patients seemed to be similarly interested in being enrolled to prevent a complication from pregnancy as in treating one. These results supported the concept that most individuals in the obstetrical RCTs represent the eligible population.
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