Researchers at Cardiff University are asking families in Wales, who have had babies born prematurely, for their help.
They want ask the parents if their children have had any breathing and health related problems, and also to ask about the child's developing and learning.
Researchers say this will help them to establish if children born only moderately prematurely need to be followed more closely during childhood "than has occurred until now."
In Wales, there are about 35,000 babies born each year and from these about 2,500 are born prematurely.
There has been a lot of research demonstrating the negative effects that extreme premature birth can have on the lung function of children, but there's limited data on the lung function of moderately preterm born children, especially as they grow older.
More top news
Welsh children are falling behind in the happiness stakes because they spend too much time indoors.
Aaron Ramsey says Wales can exploit England's weaknesses when the two countries meet at Euro 2016.
David Cameron could call for extension of EU tariffs.