If your search retrieved too few citations, here are three strategies to expand your search.
1. Find related articles. Open a useful citation in abstract view, then click the Similar articles "See all" link to display a pre-calculated set of PubMed citations closely related to the article.
2. Try alternative search terms to the ones you used. Try to find a MeSH term for your topic. (Learn more.)
The search for 'parental bonding NICU' brings up fewer than 40 articles. However, the search for 'parent-child relations neonatal intensive care unit' retrieves over 400. See how PubMed ran this search in the details box below.
Adding a term, such as breastfeeding or holding will retrieve a very specific smaller subset of useful articles the first search missed.
3. Remove extraneous or specific terms to broaden your search.
If your search, facial pain sleep disorders, retrieves too few citations, consider removing search terms to broader the search and retrieve more citations. For example, try pain sleep disorders.