Women who regularly use standard hairspray more than double their chances of having a baby with a defect.
The number of babies born with hypospadias - where the urinary tract grows abnormally - has risen sharply in the last 20 years, and researchers believe the increase may be due to the mother's exposure to chemicals called phthalates, which are found in plastics and hairsprays.
Phthalates disrupt hormones, and they have been banned in toys sold in the EU, and they have also been removed from most hairsprays and cosmetic products since 2005.
Researchers from Imperial College London interviewed 471 women who had given birth to children with hypospadias in 1997 and 1998. Around half the women had been exposed to high levels of hairspray through their work as hairdressers compared to women who had given birth to healthy babies.
(Source: Environmental Health Perspectives, 2008; 116: 1509-118).