The above spreadsheet shows how such a probability might accumulate over a year and a half, until it becomes extremely likely that a healthy woman would get pregnant.
A typical doctor would probably suggest that the couple try to conceive their baby "naturally", rather than recommending a medical intervention after only a couple months.
Also read my "Math Estimates How Long to Get Pregnant" for more advice on using the math, and on what to consider before searching for a fertility clinic to help you to conceive your baby. Although I would normally "preview" the images that I make for an article, this time it's a "postview" since Decoded Pregnancy has already gone to press...I mean, published online.
One Untimely Writing Tip
Although I'm sure there will be no repercussions, it was a mistake to forget to pre-publish these images here.
I was busy enough with other tasks that this slipped, even though I'd planned the title as a "preview".
While "no harm, no foul" makes for a more relaxed sporting event, it's not an excuse in the business of writing.
On the other hand...read the articles to get a much better sense of the importance of timing when you want to get pregnant!