I believe a number of statements from this supplement to WP:OR are relevant to this discussion:
Obvious deductions are not original research.  This includes simple logical deductions. For example, if A is in district B, and district B is in province C, then A is in province C. This is a simple syllogism. Included are all of the other simple deductions. It is an obvious deduction that Lea's Shield is the same class of device as the FemCap.
Identifying synonymous terms, and collecting related information under a common heading is also part of writing an encyclopedia. Reliable sources do not always use consistent terminology, and it is sometimes necessary to determine when two sources are calling the same thing by different names. This does not require a third source to state this explicitly, as long as the conclusion is obvious from the context of the sources. U.K. sources use the term "cervical cap" to refer to multiple devices available in that country .  Many older U.S. sources use the term "cervical cap" to refer exclusively to the Prentif device (here effectiveness results for Prentif are labeled only "cervical cap").  A few current U.S. sources (such as those cited by David) use the term "cervical cap" to refer exclusively to the FemCap device.  Some U.S. sources include the Lea's Shield under the cervical cap umbrella.  These are obviously inconsistencies in terminology, and they can be resolved by the judgment and consensus of editors on Wikipedia.
Although the English language version of a source should be used when it is published in multiple languages, foreign language sources are also welcome, and even encouraged to reduce systemic bias. Non-English sources identify the Lea's Shield as a cervical cap.
Sources may be written in a fictional, nationalistic, religious or other narrow context. Material from these sources incorporated in Wikipedia must be placed in a broader, more encyclopedic context. Placing material in an encyclopedic context is different from taking things out of context. For example... material written from a localized or nationalistic perspective must be presented in a perspective consistent with a world-wide viewpoint... This is not original research when good editorial judgment is used. Taking material from the U.S. - where only one cervical cap (first Prentif, then later FemCap) was available for many decades, and so "cervical cap" is synonymous with a single device - and presenting it in a perspective consistent with a world-wide viewpoint where multiple cervical caps are available at the same time, and so the definition of cervical cap is broader and includes Lea's Shield, is allowed and even encouraged on Wikipedia.

I am not attached to the title of "cervical cap" for this article.  I believe the best editorial decision would be to merge Lea's Shield into this article, but, like David and Una, I am open to looking for a new name.  Anon, are you willing to consider a merge with a name change?  If so, we can discuss alternatives to "cervical barrier", which you have objected to. Talk     C