Lunch with my pregnant sister, how to cope?

Vanessa
This week my mom, cousin and I are having lunch with one of my sisters. My husband and I have been trying to become pregnant for several years (3). My sister has been married for 1 year and she and her husband got pregnant after trying for 1 month. 
​Originally this lunch was just supposed to be my cousin and myself . This morning I was informed that my pregnant sister is also coming to lunch. Any idea's/suggestions on how to deal with a lunch that is now going to be all about my pregnant sister?
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