Demi Lovato has hit out at gender reveal parties for being "transphobic".

In an Instagram post, the 28-year-old Sorry Not Sorry singer shared her thoughts on the concept, which is hugely popular among expectant parents, as she re-posted a comment made by transgender rights activist Alok Vaid-Menon.

The post says that it’s, “both insincere and incorrect to pretend that gender reveal parties are not transphobic."

“This is not about political correctness, it’s just … correct,” continues the message. “We condemn gender reveals not because of our identity, but because of reality. Gender reveals are based on the illusion that genitals = gender and that there are only two options ‘boy or girl’.”

It adds: “This definition erases the fact that there are boys with vaginas and girls with penises and that there are people who are neither boys nor girls. The idea that sex is based on genitalia is inconsistent with science.”

In her own comment beneath the post, the Skyscraper star penned: "@alokvmenon with the real (prayer and heart emojis) Thank you for sharing your knowledge and educating us always. (sic)"