Pregnant women who use nicotine patches and gum to help kick off their smoking habit are putting their unborn babies at risk, scientists have said.
They said the foetus absorbs the addictive substance and this can cause high blood pressure and heart problems later in life.
"We have found distinct links between cigarette smoking or even using nicotine patches or gum and the long-term harm for the child," the Daily Mail quoted Dr DaLiao Xiao, from the Loma Linda University School of Medicine in California, as saying.
The American researchers suspect that nicotine causes harmful chemicals to form in the babies' blood vessels while they are still in the womb.
These chemicals, known as reactive oxygen species, permanently damage the blood vessels so they are unable to function properly, which can lead to high blood pressure and heart problems.
Women who smoke are strongly urged to give up during pregnancy as the cigarettes harm the baby putting them at much higher risk of cot death, being born premature, deformaties and illnesses in childhood.
The study was published in the British Journal of Pharmacology.