"I feel in order to have a real conversation about motherhood, you need to share truths and talk about what's really going on," the star tells PEOPLE

“I’m very candid in this book, very vulnerable,” says Laura Prepon of her new guide to motherhood, You & I As Mothers. “I’m a private person so this is the first time I’ve been this open. But I feel in order to have a real conversation about motherhood, you need to share truths and talk about what’s really going on.”

Among the revelations is her story of having to terminate her second pregnancy.

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After Prepon and husband Ben Foster had their daughter Ella in 2017, the Orange Is the New Black actress became pregnant again in 2018. Eager to share the news with loved ones, she and Foster held off until they scheduled a sonogram at 16 weeks.

When the sonographer looked at the screen, Prepon immediately knew something was wrong. After her ob-gyn was summoned, she told her it could be a condition called cystic hygroma (an abnormal development of the lymphatic vascular system during embryonic growth).

After an echocardiogram, the condition was confirmed. “Our neonatal specialist told us the brain was not growing and the bones were not growing,” says Prepon. “We were told the pregnancy would not go to full term and that my body was at risk carrying any longer.”

“Ben held me as I cried,” she says. “We had to terminate the pregnancy.”

Image zoom The actress with her baby

The pain of losing the baby also brought back feelings of self loathing that had long plagued Prepon, feelings often masked by the bulimia she had suffered from 15 years old until her late 20s. (A story she also tells in the book.)

“To get to the second trimester and then be told this awful news, I felt like a failure,” she says. “I felt like my body had failed and failed having another baby. The whole cycle of what’s wrong with my body came back.”

“I was scared that somehow the abuse I put my body through could have been part of the reason things went wrong,” she says. “Doctors confirmed it wasn’t but in those moments it’s easy to punish yourself.”

Worried she would not be able to get pregnant again, Prepon leaned on her husband for strength as they mourned the loss.

“He was so supportive,” she says. “It got to the point where I didn’t know if I was going to be able to get pregnant again because the healing process took so long. But my husband knew we would be able to have a healthy sibling for Ella.”

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When she shared the story of losing the pregnancy with close friends, she was moved by the response. “I began hearing of others who had gone through something similar and I realized I was not alone.”

Finding out she was pregnant again last year, brought happiness — and fear. “I couldn’t fathom going through it again,” says Prepon. “When the news began to sink in, we realized we’re going to go on this journey again and bring our daughter a sibling.”

“I was also ecstatic,” she says. “I mean, it’s magical.”

“It made me so thankful for the blessing we have now,” she says of their baby boy born at the end of February. “It put into perspective what a blessing it is to have a healthy child.”