I know this sounds like a given but often times we are not very present to each other. Know your audience. If you know someone at that party, women's group or gathering is living with infertility or recently experienced the death of their unborn child be aware of what you are saying. Think before you speak, especially if you are going to vent about pregnancy or child rearing. It's not to say you should not be able to share your struggles but if you are in a group setting and you know the other women will jump on the venting band wagon perhaps that comment or venting should be kept best for the mom's group you go to. If we are really present in our conversations we are aware of what we and others are saying and be cognizant of how others are reacting to the conversation.
Redirect the Conversation
If you notice the conversation is all about child rearing or venting about said subject try and redirect the discussion. Tact is needed for this because you don't just want to shout "be quiet y'all so and so is uncomfortable." That would be super embarrassing for the infertile and the redirector! Maybe changing the subject when it would be appropriate for you to add something. Talking about the seasons or favorite recipes you have been making or crafts you have been working on or the show you are binge watching at the moment or the good deals you've found on women's clothing are great subjects all women can relate to.
This is not to say children should not be discussed at all, of course they will be talked about because you have children! I appreciate my friends sharing the realities of raising children because I don't want to idolize parenthood and look at it through rose colored glasses but I prefer that sharing to be one on one so we can both share our struggles. If I am the only one not raising children in the conversation all about child rearing/pregnancy then I feel like I am wearing a scarlet "I" and infertility feels really isolating.
Seek Them Out
If you were not successful at changing the subject and you know your friend was uncomfortable then seek them out some time during or after the gathering. Ask them how they are doing, how's work or their ministry. Infertile women often feel ignored by their peers so making that effort to acknowledge someone can be very affirming. If you know them well enough you can ask how their treatment or adoption/foster care is going. If you don't know them that well then stick to the basic subjects of common interest. Let them know you are praying for them and if they have any prayer requests then to let you know.
So that's my advice from an infertile woman's perspective. What I have to remember is that most often when I am in a group of married women is that most if not all of them will have children. I feel so awkward trying to contribute to the conversation if it's all about child rearing because I am not raising any children, although I know a lot about child development, it's OK if I have nothing to say. Even though we are living out our vocations differently at the moment I find great comfort in relating to my women friends whether they are married or single. I love when we can all build each other up even if we can't relate exactly to what each other is going through. So as we are going into the various holidays soon hopefully there will be more fellowship and fun rather than awkward isolating moments.