Meghan Trainor Mistook Early Pregnancy Symptom for Her Period

Moments before appearing on "The Tonight Show Starring Jimmy Fallon" in October 2022, Meghan Trainor—clad in all white—got her period.

Or so she thought. The singer was so confident she'd started menstruating, she posted a video on TikTok with the caption: "When you get your period at sound check at Fallon." During the show, Trainor even announced, "Auntie Flow is here," to host Jimmy Fallon and audience members.

Trainor reveals second pregnancy

Fast-forward to Jan. 30, when Trainor revealed the big news on "Today": She's pregnant; four months pregnant, to be specific.

If you think the math on her timeline doesn't quite check out, you're not alone. Trainor herself was confused.

"I didn't know [I was pregnant] because I bled in the beginning of this pregnancy to the point where I thought there were periods," Trainor explained in an interview with People released Feb. 1. "So when I found out how far along, I was like, 'What? No, I just got pregnant and how am I that far?'"

Eventually, the pop star realized she hadn't gotten her period on Fallon's show after all.

"That was me implanting," Trainor explained. "I was making motherf---ing life. I was making life during my sound check at Fallon."

About implantation bleeding during pregnancy

"Implantation bleeding happens as a first sign of pregnancy after your egg is fertilized with sperm," said Monte Swarup, M.D., an OB-GYN in Arizona and founder of HPV Hub. "The egg and sperm become an embryo. The embryo attaches and this can cause light bleeding."

Not everyone experiences implantation bleeding during pregnancy. The American Pregnancy Association estimates about one-third of pregnant people experience the phenomenon.

Implantation bleeding is distinguishable from period bleeding in a few key ways, Swarup said.

"Implantation bleeding will only last one to two days," he explained. "Also, you won't see any tissue or blood clots, unlike your period."

Trainor writes a book about new motherhood

How to distinguish period bleeding from implantation bleeding is exactly the kind of information Trainor wishes she'd been taught before becoming a mother.

Feeling in the dark about certain elements of first-time motherhood inspired Trainor to write the book "Dear Future Mama: A TMI Guide to Pregnancy, Birth and New Motherhood." The memoir, set to be released on April 25, features Trainor detailing her first pregnancy experience with her son, Riley, who turns 2 on Feb. 8.

"It's the book I wish I had when I was pregnant so I wouldn't feel so alone or so weird or so 'What's wrong with my body? Is this normal? How am I supposed to feel?'" Trainor told People. "I'm an open book, and I love telling everybody everything about my grossness and all my truths."

In the book's pages, Trainor shares personal stories about body image, mental health and balancing a career with motherhood, as well as insights from professionals.

"I know not everyone has access to the amazing people that I have access to," Trainor said in the People interview. "So my dietitian is in the book and gives advice for every trimester. My trainer is in the book, and there's pictures showing you what you can do for workouts, because you can still work out when you're pregnant, and it's safe—I didn't know that. And my OB-GYN is also in the book all over the place giving advice."