"People variously go through the grieving process and try to figure things out," he said. "It's fair to wait a reasonable amount of time, at least a year, and as the grief passes and you learn to live with the fact the person is gone, you can start looking forward."
As for the Travoltas, not only are they dealing with the still-fresh loss of their son Jett, but their dogs were accidentally killed by a truck on a Bangor, Maine, airport runway just this last week.
"Kelly Preston's pregnancy is a huge shocker," said Heidi Parker of Star, who broke the story. "It's a big deal in Hollywood because it's almost like the perfect movie; they had a terrible loss now they're having a miracle in their lives."
"They've suffered a lot in the last year," she said. "They've been grieving. They've had a very difficult time."
Other parents who have lost children say the grief really never does go away, regardless of subsequent pregnancies.
Natasha Clarke, a British singer and Vogue model, had a second son in 2009 after losing her infant daughter Ava to a rare genetic condition, methylmalonic acidaemia, which doesn't allow a child to break down proteins.
'I am so grateful to have two healthy boys but you never get over the death of a child," she told Britain's Daily Mail newspaper. "When you carry them for nine months, you are planning their future and thinking about their name and how they will fit into the family."
'On Ava's second birthday, I sang happy birthday to her picture," she said. "I will never watch my little girl go to school. Losing a child is like losing part of yourself. You learn to live with it but you never get over it.'