"It wasn't exactly planned," Laura, 33, tells PEOPLE of the pregnancy, "but you get separated from your husband for five months, not knowing if you will ever see him again and certain things happen!"
The child is due in a few weeks – and Laura and husband Iain Clayton, 43, couldn't be happier.
"We feel like this child is a miracle," she says. "I had pushed [motherhood] off for so long, I was so focused on my career, even though I knew my husband was ready. And so the fact that we had the opportunity to try, and it even happened ... it's such a blessing."
To honor her sister, "We are going to name her Li, after Lisa," Laura says. "She's really excited to be an aunt."
Finding Her Voice
Ling and fellow American journalist Euna Lee were arrested in March 2009 after crossing into North Korea. They were sentenced in June but released in August after appeals from Lisa Ling and former president Bill Clinton.
For a long time, Laura didn't speak about her time in captivity. But now she and Lisa, 36, have co-authored Somewhere Inside, a memoir of Laura's experience, Lisa's efforts to get her freed and the sisters' bond with each other.
"Just hearing from my sister [while in prison] gave me tremendous hope and strength because I knew she was doing everything in her power to get me home," Laura says. "We are so close; we have developed a really special bond and kind of almost a special language where we don't have to use a lot of words to understand what the other is trying to convey."
Laura and Euna Lee also appear together on their own network in a special currently featured online on Current TV's Web site. For much more, including an excerpt from the Lings' memoir Somewhere Inside and exclusive photos of the sisters, pick up the new issue of PEOPLE, on newsstands Friday