'This Is Us' season 1 episode 12 news, spoilers: Rebecca prepares for birth of her triplets; Fox chairman explains title's move to NBC

Rebecca, who is portrayed by Mandy Moore, will be too excited for the birth of her triplets that she forgets that it's her husband's birthday. Meanwhile, Fox gave "This Is Us" to NBC, and network co-chairman Gary Newman explained why.

In the upcoming 12th episode of "This Is Us," titled "The Big Day," Rebecca will soon be giving birth to her triplets. This put her in an overwhelmed mix of emotions that she forgets that the birthday of her husband, Jack (Milo Ventimiglia), is also approaching.

The episode's synopsis reads: "As the birth date of her triplets quickly approaches, a frazzled and emotional Rebecca forgets Jack's birthday. Dr. K (Gerald McRaney) struggles with the loss of his wife and wonders how he'll be able to continue on with his life without her. The firefighter who delivered baby Randall to the hospital - fights to save his marriage."

Fans will also see the defining moment when William (Ron Cephas Jones) left Randall at the hospital, which fulfils his fate as one of Jack and Rebecca's triplets.

Although there is no word about it, Kate (Chrissy Metz) and Toby's (Chris Sullivan) relationship might also be featured in episode 12 since they recently had a big moment in their relationship — they decided to get married just after the two got a huge scare that Toby might be dying.

Meanwhile, "This Is Us" recently moved from Fox to NBC, and Newman shared at the Television Critics Association press tour why the show would do better with their competitor.

As Los Angeles Times reported, "We have made a commitment to our writers at our studio that we're going to give them the greatest chance to succeed. When we read that script we just felt that tonally it was a show that seemed consistent with 'Parenthood' and 'Friday Night Lights' and NBC had some real success with that," Newman explained.

"This Is Us" season 1 is scheduled to air every Tuesday night at 9 p.m. EST on NBC.