The case-control study involved 3,690 women who had given birth to children with congenital heart defects and 4,760 mothers of healthy infants.
Accounting for confounding factors, including maternal smoking and age, researchers looked at whether there was any link between UTI in the first three months of pregnancy or the month before conception and congenital heart defects in the infant.
An association was found for a condition called hypoplastic left heart syndrome (HLHS).
This potentially fatal condition means children have to have three operations before the age of three, if they are to have a chance of survival, said lead researcher Dr Sadia Malik from Arkansas Children's Hospital.
The condition affects around one in 1,000 pregnancies. But Dr Malik found maternal UTIs in early pregnancy increased the risk 1.7-fold.
The findings highlighted the need for early detection of STIs in women of reproductive age.
'GPs should order urine tests for pregnant women to ensure they aren't harbouring the infection,' he said.
AHA scientific sessions 4-7 November 2007, Orlando, Florida
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