When a healthcare professional says natural history...

When a healthcare professional says the words "natural history", they don't mean the textbook definition. Usually Natural History refers to a field of study which scientists pursued back in the 1800s, exploring the natural world. Eventually this became biology and geology.

However, when a healthcare professional refers to the natural history of a disease, they mean what the disease looks like over time, especially if untreated.

If you're really lucky, you can search "natural history"[all fields] and combine it with the MeSH best describing your disease. You might get one or two results.

If you search "Natural History"[Mesh], you'll get the official definition, which is of no use whatsoever.

You can try "Prognosis"[Mesh], which will almost certainly give results when combined with the MeSH for your disease. However, since "Treatment Outcome"[MeSH] is a narrower term of "Prognosis"[Mesh], you may wish not to explode: "Prognosis"[Mesh:NoExp].

The best MeSH for this concept is "Disease Progression"[Mesh], a very useful-sounding MeSH that one can only find by stumbling across it by accident. Again, if you're lucky, combining this MeSH with your disease MeSH will produce a couple of results. However, "Disease Progression" is one of what I call the "Weird MeSH" - that is, highly useful but often overlooked by indexers and searchers alike.

In some cases, "Watchful Waiting"[Mesh] OR "Conservative Treatment"[Mesh] can be useful. Conservative Treatment was added as a MeSH in 2017, and will likely be a "Weird MeSH", so keywording can also be useful: conservative*[tiab] OR nonsurg*[tiab] OR non-surg*[tiab] OR nonoperati*[tiab] OR non-operati*[tiab]

Sometimes "Survival Rate"[Mesh] OR "Disease-Free Survival"[Mesh] are useful too.

In PubMed, the following keywords may be useful:
prognosis[tiab] OR outcome*[tiab] OR "natural history"[tiab] OR "disease progression"[tiab] OR "disease course"[tiab] OR "disease evolution"[tiab] OR "disease trajectory"[tiab] OR "clinical progression"[tiab] OR "clinical course"[tiab] OR  "clinical evolution"[tiab] OR "clinical trajectory"[tiab] OR "natural progression"[tiab] OR "natural course"[tiab] OR "natural evolution"[tiab] OR "course trajectory"[tiab] OR "benign neglect"[tiab]

If all else fails, you can try a full text search where available.

Medline EBSCO:

TX "natural history" AND MH "Disease Name+"
TX disease N3 progress* AND MH "Disease Name+"
TX clinical progress* AND MH "Disease Name+"
TX natural course AND MH "Disease Name+"
TX natural evolution AND MH "Disease Name+"
TX course trajector* AND MH "Disease Name+"

Google scholar:

"disease name" "natural history"

EMBASE:

disease course/ or exp deterioration/ or exp disease clearance/ or exp disease duration/ or exp disease exacerbation/ or exp general condition deterioration/ or exp general condition improvement/ or exp illness trajectory/ or exp prognosis/ or exp recurrent disease/ or exp reinfection/ or exp relapse/ or exp remission/ or exp survival/

if it's a cancer thing:
exp cancer growth/ or exp cancer inhibition/ or exp cancer recurrence/ or exp cancer regression/ or exp leukemia relapse/ or exp leukemia remission/ or exp metastasis inhibition/ or exp tumor growth/ or exp tumor recurrence/ or exp tumor regression/

 PsycInfo:

 DE "Disease Course" OR DE "Prognosis"

Keywords for a title and abstract search:
prognosis OR outcome* OR natural history OR disease course OR clinical progression OR clinical course OR clinical evolution OR clinical trajectory OR natural progression OR natural course OR natural evolution OR course trajectory OR benign neglect
disease N3 progress*
disease N3 evolution*
disease N3 trajectory

Entry term is "course of illness"
Narrower term of "Disease Course" is Metastasis.