A moat, per Dictionary.com, is a deep, wide trench, usually filled with water, surrounding the rampart of a fortified place, as a town or a castle.
Some people, when going through infertility, need to seclude themselves while undergoing their journey to parenthood. These are the people who will only share information as they feel others in their life need to know. So, they create an emotional "moat" as they undergo their treatments. This oftentimes doesn't bode well with the people being shut out, but it is not your responsibility to make them comfortable. You need to focus on you right now.
Conversely, there are others going through infertility, who can't share enough with the people closest to them. These are the people who try & fit all of the supportive people in their life into their proverbial life boat, in order to get through the process. The more support, the better.
Whichever group you fall into, recognize that it is in YOUR control to invite or dis-invite anyone to help you through this journey. If you have an overbearing mother (or mother-in-law), a nosy sister who gossips, a competitive friend who has to "one up" you....whatever the kinds of people in your life, YOU decide who gets to ride this wave with you or not.
Maybe you are the type who has everyone in your life boat in every other area of your life, but now that you're undergoing fertility treatments, you need to create a moat of self-protection, in order to survive everything. Or vice versa. Whatever your situation, know that this is an area where you DO have control. Infertility is by nature out of your complete control, so gaining control wherever you can, is paramount.
Focus on the task at hand. Become a parent, or not, however you need to. If there are people in your life who will be there at the end, they will need to learn to let you call the shots on your way there.