In the snap, Luddington wears an almost identical bra and underwear set that Beyoncé wore in the now-famous pic she posted to social media earlier this week to announce that she was pregnant with twins.
"Arguing over whether this is really necessary..... ," Luddington, 33, captioned the photo, which also features her co-star Ellen Pompeo.
One day earlier, Luddington revealed the sex of her baby via Instagram, posting a sweet photo of herself holding a onesie emblazoned with the words, "Tomb Raider in training."
"I am so excited to announce today that I am having a... girl!" she wrote. "I want her to grow up knowing how strong women are ?. To be a little warrior who is not afraid to use her voice and stand up for what she believes is right. To navigate through life with courage and kindness, and to be one of the girls who says "you CAN sit with us..". Special shoutout to #crystaldynamics for sending me her first #tombraider onesie ?"