Impregnable /ɪmˈprɛɡnəbəl/ adjective
1. | strong enough to resist or withstand attack; not to be taken by force, unconquerable: an impregnable fort. |
2. | not to be overcome or overthrown: an impregnable argument. |
Inconceivable doesn't mean (a woman) cannot conceive.
Inconceivable /ˌɪnkənˈsiːvəbəl/ adjective
1. | unimaginable; unthinkable. |
2. | unbelievable; incredible. |
Unbearable doesn't mean (a woman) cannot bear children.
Unbearable /ʌnˈbɛərəbəl/ adjective
1. | not able to be borne or endured |
{ Definitions taken from http://www.dictionary.com }