Sarah Brown has said it is "very uplifting" to know research that stemmed from the death of her baby daughter helped save a grandchild of Labour leader John Smith.
The wife of former prime minister Gordon Brown told the Daily Mirror that losing 10-day-old Jennifer after she was born at 33 weeks in 2002 was a "very intense time".
She set up charity PiggyBankKids (now Theirworld), which established the Jennifer Brown Research Laboratory (JBRL) at the University of Edinburgh in 2004.
The JBRL looked at ways to help premature babies thrive, including research into how much oxygen should be given to babies in incubators.
Almost 15 years later, the research helped to save the life of Ella McConnachie - the granddaughter of the late Labour chief who counted Mr Brown as one of his closest political colleagues.
Ella's mother, Catherine Smith, told the paper: "What Gordon and Sarah have done is the most extraordinary gift. They've given us our daughter."
Ms Smith, from Dundee, had an emergency Caesarean section after developing HELLP syndrome, an aggressive form of pre-eclampsia.
Ella, now aged two, weighed 1lb 10oz and for weeks was kept in an incubator fitted with an oxygen level monitor, as part of JBRL's research.
Ms Smith said: "I wrote to Sarah to say, 'I want you to know how grateful I am. I can seen how your sadness is now helping Ella'.
"I could see the incredible care Ella was getting and she was going to survive, and all because of what Gordon and Sarah had done."
She said Ella's late grandfather would find it "incredibly moving what Gordon has done for our family".
Ms Smith is now working with Mr and Mrs Brown to raise awareness of JBRL's work.
Mrs Brown, 53, told the Mirror: "You don't wish this on anyone, and you certainly don't wish it on yourself, but I look for the good I can do, and ensure we contribute to a body of knowledge so more mysteries are unlocked and there are more possibilities for happy outcomes.
"It's very uplifting to know somebody has gone home with their baby thanks to the work of the lab created in Jennifer's memory.
"And this translates itself through to many other families who've also been able to take their babies home. To know if you can do good for one person it's enough. But if it can go beyond that then it's even better.
"And having a personal connection – as we do with Catherine and her family – to someone where the outcome has changed, is wonderful."
She added: "I'm very grateful for the two boys I do have. They make all the difference in the world, but neither Gordon nor I are ever going to forget Jennifer."