Naomi Watts was pregnant with her second child, and there's a scene at the clinic where the audience can see her real son moving inside her belly. Naomi said in an interview that the baby was sleeping and she took a cold glass of water to wake him up inside.
Despite playing mother and daughter on film, in reality, Annette Bening is only ten years older than Naomi Watts. Nevertheless, Bening's character got pregnant at fourteen, so their age difference shouldn't be much more anyway.
The trivia item below may give away important plot points.
When Karen (Annette Bening) learns about Elizabeth's (Naomi Watts') daughter (her granddaughter) near the end of the film, she learns the baby's name is Ella. Ella is also the name of Bening's youngest child in real-life.