One strategy that can make your research run more smoothly is the use of subject headings, like Medical Subject Headings (MeSH). Subject headings are liek hashtags applied to articles when they are ingested to a database, and identify all the "subects" in each article. For example, you could do one search for articles with the subject heading "Carbonated Beverages," instead of searching for all variations of the word "pop" (i.e. "soda," "coke," "soft drink").
Most databases make their own brand of subject headings; PubMed uses "MeSH" (Medical Subject Headings), but CINAHL uses "CINAHL headings". They work the same, but are formatted differently.
("Maternal Health"[Mesh] OR "Pregnancy"[Mesh] OR "maternal morbidity") AND ("Mental Health"[Mesh] OR wellbeing)
In the example above, the subject headings have "Mesh" in brackets after the headings, which is an acronym for "Medical Subject Headings", the proprietary subject headings used on PubMed.
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