Ronda Kaysen: When John Travolta and Kelly Preston announced that they're expecting a new baby, many hailed the news as a blessing for a family that has endured such an unspeakable loss. After all, isn't a baby a wonderful thing? A child who will fill the void left behind after the sudden death of their 16-year-old son, Jett, last year? Some psychologists, however, aren't so sure that a new baby is always the right thing for a family reeling from grief.

It's not uncommon for a family that has lost a child to have another child. The practice is so common, in fact, that psychologists have coined a term for it -- "replacement child" -- and some warn that having a baby after losing a child isn't always a good idea.

"The idea of replacement -- that people are replaceable like lightbulbs -- it's a devastating myth," Russell Friedman, executive director of the Grief Recovery Institute (which provides recovery training), told CNN. "Is it OK to have other children? Yes. Is it always the smartest to do right away? No. The truth is, you have to grieve the children who died."

CNN profiled Judy Mandel, author of the memoir, "Replacement Child." She described a childhood spent living in the shadow of a sister who died before she was born. Her parents often dressed Judy in her sister's clothes and compared her to a sister she could never replace.

"It was almost like a legend," she said. "There's the aspect of being in the shadow of that. You can't live up to that promise the child had. I was always told what a special child she was, how promising she was in school, how perfect she was -- it's tough. I was thinking, 'I can't be as good as that.'"

Dr. Cara Gardenswartz, a clinical psychologist and momlogic advisor, says that there are things parents like Travolta and Preston can do to thwart these risks. First and foremost is to face the grief head-on.

"There's going to be all kinds of mixed feelings, and that's what happens when there's grief," she says. "It's all about how it's dealt with, how it's talked about. It's all about the open, honest communication."

Parents who've lost a child have another baby for many reasons, Gardenswartz says: They have more love to give; they want to bring a new child into the world and they want to expand their family. A new baby can bring real joy to a family rocked by grief. If the parents are mindful to frame the new birth in that context -- and not hide from the loss -- then the new child can truly be a blessing.

The person who will likely have the hardest time with the new addition is the couple's 10-year-old daughter, Ella. As a child, she's likely to feel guilty and worry that her parents' decision to have another child means that she's not good enough.

Gardenswartz says that, again, the best way to combat these feelings is through open communication. "The key is keeping that kid from the media," she says. "That's what makes their situation more complicated than anything else."