When Meredith walks out she passes Bailey, who calls out gruffly the same instructions not to sit down at the wedding. Meredith just looks confused but doesn't seem to question it. I have to assume Callie handled telling her the actual details later.
Cristina is looking at some scans when Owen comes in and tells her that the lawyer will be sending over papers the next day. She tells him that she already signed a whole pile of lawsuit stuff and is taken aback when he tells her that these are their divorce papers, since it seems to be proceeding so quickly. He asks her if it's a problem for her to sign tomorrow and she has a bit of an edge to her voice as she chirps that it's fine. It's only the dissolution of their marriage, after all.
In a nice callback to seasons of yore, there's a loving shot of a ferry boat before we see Mere and Derek in the doctor's office for her secret ultrasound appointment. Derek mentions that he would like to tell Lizzie about the pregnancy but Mere is sure she'll tell the whole family and doesn't want that. (Why throw her a bone? She's only donating her nerves, after all.) Through this it comes out that Mere hasn't even told Cristina yet, and Derek is shocked, to say the least. Mere tells him clinically that there's no point since she's probably going to miscarry anyway given her angry uterus, and she's just being realistic. Derek is not my favorite guy in the world, but my heart breaks for him a little because he's so saddened by this. When the doc comes back in he pointedly asks if there are things they can do to help the pregnancy given their history and she happily assures them that there are, and she'll be keeping a super close eye the whole time. Derek holds Meredith's hand as the doc gets to work and then they hear what seems to be a strong little heartbeat. Derek is happy, but Meredith's face never changes, and she finally just looks away. Poor Dr. Simpson seems to be the most excited one in the room.